[PROF-9147] Document workaround for Ruby gc_finalize_deferred

[ivoanjo]

What does this PR do? What is the motivation?

This PR updates the Ruby troubleshooting documentation, now that a new workaround exists and is auto-applied (https://github.com/DataDog/dd-trace-rb/pull/3473).

This clarifies that using the "no signals" workaround is no longer the recommended way to solve this issue.

Merge instructions

• [x] Please merge after reviewing

The dd-trace-rb release containing the fix (1.21.0) has not yet been released, so I'm queuing this documentation change but ask that we don't merge it yet, and I'll come back and leave a note once the release is out.

Additional notes

N/A

[github-actions[bot]]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/ivoanjo/gc-finalize-deferred-document-workaround/profiler/profiler_troubleshooting/ruby

[ivoanjo]

Version https://rubygems.org/gems/ddtrace/versions/1.21.0 is now out, this is ready for review/merging :)

[ivoanjo]

Thanks for getting this one merged :)