Align simplecov version usage

[TonyCTHsu]

What does this PR do?

Align simplecov version usage

Motivation:

From: #4263

Gemfile definition for simplecov without constraint causing 0.21.2 and 0.22.0 installed across different groups.

Change log entry
None.

[github-actions]

Thank you for updating Change log entry section 👏

^{Visited at: 2025-01-10 15:29:48 UTC}

[datadog-datadog-prod-us1]

Datadog Report

Branch report: tonycthsu/align-simplecov-version
Commit report: 7a50b66
Test service: dd-trace-rb

✅ 0 Failed, 22124 Passed, 1477 Skipped, 5m 27.42s Total Time

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (7c02a1c) to head (7a50b66).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4278   +/-   ##
=======================================
  Coverage   97.72%   97.72%           
=======================================
  Files        1354     1354           
  Lines       82419    82419           
  Branches     4220     4220           
=======================================
+ Hits        80540    80544    +4     
+ Misses       1879     1875    -4     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-10 16:00:42

Comparing candidate commit 7a50b66 in PR branch tonycthsu/align-simplecov-version with baseline commit 7c02a1c in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.