Fix example for custom server SSR caching

[sphilee]

Fixes #16725 based on this comment: #16725 (comment).

[ijjk]

Stats from current PR

Default Server Mode (Decrease detected ✓)

General

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
buildDuration	10.3s	10.5s	⚠️ +223ms
nodeModulesSize	90.5 MB	90.5 MB	✓

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.009	2.109	⚠️ +0.1
/ avg req/sec	1244.48	1185.44	⚠️ -59.04
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.049	1.156	⚠️ +0.11
/error-in-render avg req/sec	2383.1	2163.42	⚠️ -219.68

Client Bundles (main, webpack, commons)

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
677f882d2ed8..1f3c.js gzip	11.2 kB	11.2 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-be398bc..d262.js gzip	7.33 kB	7.33 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	58.3 kB	58.3 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
677f882d2ed8..dule.js gzip	7.02 kB	7.02 kB	✓
framework.HA..dule.js gzip	39 kB	39 kB	✓
main-378f0c6..dule.js gzip	6.33 kB	6.33 kB	✓
webpack-07c5..dule.js gzip	751 B	751 B	✓
Overall change	53.1 kB	53.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
polyfills-b5..1119.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_app-9a0b9e1..b37e.js gzip	1.28 kB	1.28 kB	✓
_error-ed1b0..8fbd.js gzip	3.44 kB	3.44 kB	✓
hooks-89731c..c609.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-a674d88..ccde.js gzip	1.35 kB	1.35 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	7.75 kB	7.75 kB	✓

Client Pages Modern

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_app-75d3a82..dule.js gzip	625 B	625 B	✓
_error-4469a..dule.js gzip	2.29 kB	2.29 kB	✓
hooks-cbf13f..dule.js gzip	387 B	387 B	✓
index-b9a643..dule.js gzip	226 B	226 B	✓
link-a4469f3..dule.js gzip	1.32 kB	1.32 kB	✓
routerDirect..dule.js gzip	284 B	284 B	✓
withRouter-f..dule.js gzip	282 B	282 B	✓
Overall change	5.41 kB	5.41 kB	✓

Client Build Manifests

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_buildManifest.js gzip	322 B	322 B	✓
_buildManife..dule.js gzip	330 B	330 B	✓
Overall change	652 B	652 B	✓

Rendered Page Sizes

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
index.html gzip	1 kB	1 kB	✓
link.html gzip	1.01 kB	1.01 kB	✓
withRouter.html gzip	994 B	994 B	✓
Overall change	3 kB	3 kB	✓

---

Serverless Mode

General

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
buildDuration	12s	12.1s	⚠️ +86ms
nodeModulesSize	90.5 MB	90.5 MB	✓

Client Bundles (main, webpack, commons)

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
677f882d2ed8..1f3c.js gzip	11.2 kB	11.2 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-be398bc..d262.js gzip	7.33 kB	7.33 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	58.3 kB	58.3 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
677f882d2ed8..dule.js gzip	7.02 kB	7.02 kB	✓
framework.HA..dule.js gzip	39 kB	39 kB	✓
main-378f0c6..dule.js gzip	6.33 kB	6.33 kB	✓
webpack-07c5..dule.js gzip	751 B	751 B	✓
Overall change	53.1 kB	53.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
polyfills-b5..1119.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_app-9a0b9e1..b37e.js gzip	1.28 kB	1.28 kB	✓
_error-ed1b0..8fbd.js gzip	3.44 kB	3.44 kB	✓
hooks-89731c..c609.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-a674d88..ccde.js gzip	1.35 kB	1.35 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	7.75 kB	7.75 kB	✓

Client Pages Modern

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_app-75d3a82..dule.js gzip	625 B	625 B	✓
_error-4469a..dule.js gzip	2.29 kB	2.29 kB	✓
hooks-cbf13f..dule.js gzip	387 B	387 B	✓
index-b9a643..dule.js gzip	226 B	226 B	✓
link-a4469f3..dule.js gzip	1.32 kB	1.32 kB	✓
routerDirect..dule.js gzip	284 B	284 B	✓
withRouter-f..dule.js gzip	282 B	282 B	✓
Overall change	5.41 kB	5.41 kB	✓

Client Build Manifests

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_buildManifest.js gzip	322 B	322 B	✓
_buildManife..dule.js gzip	330 B	330 B	✓
Overall change	652 B	652 B	✓

Serverless bundles

	vercel/next.js canary	sphilee/next.js feature/example-ssr-caching	Change
_error.js	1.07 MB	1.07 MB	✓
404.html	4.73 kB	4.73 kB	✓
hooks.html	3.92 kB	3.92 kB	✓
index.js	1.07 MB	1.07 MB	✓
link.js	1.12 MB	1.12 MB	✓
routerDirect.js	1.11 MB	1.11 MB	✓
withRouter.js	1.11 MB	1.11 MB	✓
Overall change	5.48 MB	5.48 MB	✓

Commit: df8bc75

[leerob]

I'm in favor of merging this so we can fix the broken example 👍 Thank you for contributing!