Move GA workflows from 5.2.0~beta2 to 5.2.0 release

[jmid]

Following shym/custom-opam-repository#12 this PR moves the GitHub Actions workflows from 5.2.0~beta2 to the 5.2.0 release.

[jmid]

CI summary: All 36 workflows passed 🎉

[jmid]

CI summary for merge to main:

• 32bit trunk triggered a segfault in STM Domain.DLS test sequential [ocaml5-issue] Segfault in STM Domain.DLS test sequential on bytecode #446
• linux-arm64-5.1 found a counterexample to STM Out_channel test parallel [ocaml5-issue] Out_channel.flush can cause Syserror when used in parallel #444
• linux-s390x-5.1 failed with Disconnected: Switch turned off during Lin.Internal CList int64 test with Thread
• linux-s390x-5.2 failed with Disconnected: Switch turned off during Lin.Internal CList int test with Thread

Out of 37 workflows 4 failed with 2 genuine failures and 2 CI infrastructure issues