[CI] Excessive concurrecy group

[giordano]

Why this

BumpStdlibs.jl/.github/workflows/ci.yml

Lines 13 to 15 in a7bce73

	concurrency:
	group: integration-tests-global-lock
	cancel-in-progress: ${{ (github.ref == 'refs/heads/staging') || (github.ref == 'refs/heads/trying') }}

? This doesn't even allow running CI for different Julia versions in parallel, doubling total CI time from ~15 minutes to ~30 for no reason.

[giordano]

Introduced by @DilumAluthge in #77 without a motivation.

[DilumAluthge]

Yeah, we should document why we do this. It is intentional. Our integration tests make a lot of calls to "create content" APIs such as "create a pull request". GitHub enforces "secondary rate limits" on these "create content" APIs. In the past, I had the experience (in RegistryCI and CompatHelper) that if I didn't have a global lock, then when multiple integration test ran, I'd end up hitting those secondary rate limits quite frequently. The global lock is my workaround to reduce the risk of hitting secondary rate limits.

Basically, the same motivation as JuliaRegistries/RegistryCI.jl#589

[giordano]

Basically fixed by #110 by removing the second job.