internal/ci: remove the cachePost steps

On a daily basis we evict our GitHub actions caches complete, and
repopulate using a re-run of the TryBot workflow of the tip commit (at
the time of the eviction).

Therefore, any attempt to manually prune the cache is pointless.

Hence remove the cachePost step(s).

Signed-off-by: Paul Jolly <paul@myitcv.io>
Change-Id: Ibf7473e9cff9cedca4104a70eabcb9325a3d08a1
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/551474
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

.github/workflows/trybot.yml

@@ -167,4 +167,3 @@ jobs:
 
           echo "giving up after a number of retries"
           exit 1
-      - run: find '${{ steps.go-mod-cache-dir.outputs.dir }}/cache/download' '${{ steps.go-cache-dir.outputs.dir }}' -type f -amin +7200 -delete -print

internal/ci/github/trybot.cue

@@ -82,7 +82,6 @@ trybot: _base.#bashWorkflow & {
 				_#goCheck,
 				_base.#checkGitClean,
 				_#pullThroughProxy,
-				_#cachePost,
 			]
 		}
 	}

internal/ci/github/workflows.cue

@@ -175,8 +175,3 @@ _#cachePre: [
 		}
 	},
 ]
-
-_#cachePost: json.#step & {
-	let qCacheDirs = [ for v in _#cacheDirs {"'\(v)'"}]
-	run: "find \(strings.Join(qCacheDirs, " ")) -type f -amin +7200 -delete -print"
-}