ci: add src/testing to coverage ignore patterns

[tejaskash]

Description

Add src/testing/** to coverageIgnorePatterns. These files were being counted against our coverage % but they are use exclusively for testing.

Testing

• bun test --coverage --coverage-reporter=lcov

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.65%. Comparing base (d4c31b1) to head (9ff3376).

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #1800      +/-   ##
============================================
+ Coverage     93.61%   93.65%   +0.03%     
============================================
  Files           117      107      -10     
  Lines          6708     6174     -534     
============================================
- Hits           6280     5782     -498     
+ Misses          428      392      -36     

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