core(service-worker): move to defaultPass, delete second pass

[connorjclark]

Moves service-worker to the default pass, which allows us to delete the offline pass.

I thought offline-sw-broken would fail with this change. It didn't, but then I noticed there was no assertion on the actual service-worker audit. I manually verified that the result of that audit before/after this change remained the same–it passes. I suppose we don't at all handle the case of a "Broken" SW mishandling offline requests. There's some comments in the smoke test file re: a still-open chromium bug where the InstallabilityErrors artifacts may tell us this later. https://crbug.com/1187668#c22 I assume this feature, when it finally works again, will work even without a second pass.

Fixes #11822

[connorjclark]

drive by fix

[adamraine]

Can we eliminaate this smoke condition:

lighthouse/lighthouse-cli/test/smokehouse/test-definitions/dobetterweb.js

Lines 22 to 25 in a3faef5

	networkRequests: {
	// Number of network requests differs between Fraggle Rock and legacy modes because
	// FR has fewer passes, preserve this check moving forward.
	_fraggleRockOnly: true,