Schedule our GHA Unit Tests to run every 4 hour

[sarahchen6]

What does this PR do?
This PR increases our GHA Unit Tests scheduled runs to once every 4 hour.

Motivation:
By increasing our scheduled runs, we will get a larger sample size of test runs on master -- helpful for discovering (and then addressing) flaky tests! GHA runs are free, so this should not increase CI costs.

Change log entry
None.

Additional Notes:

How to test the change?
Unit Tests on GHA will run once every 4 hour.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: sarahchen6/schedule-more-gha-runs
Commit report: a02b6e0
Test service: dd-trace-rb

✅ 0 Failed, 22270 Passed, 1477 Skipped, 5m 44.79s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-11 22:36:57

Comparing candidate commit a02b6e0 in PR branch sarahchen6/schedule-more-gha-runs with baseline commit 19519f1 in branch master.

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.74%. Comparing base (19519f1) to head (a02b6e0).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4370      +/-   ##
==========================================
+ Coverage   97.73%   97.74%   +0.01%     
==========================================
  Files        1351     1351              
  Lines       82697    82697              
  Branches     4199     4199              
==========================================
+ Hits        80827    80836       +9     
+ Misses       1870     1861       -9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.