[BUG] Fix random attribute selection in metrics foo example

[Anish701]

Fixes #4584

Changes

Update the get_random_attr method in examples/common/metrics_foo_library/foo_library.cc. Instead of random_int() % (labels.size() - 1), this PR updates it to be random_int() % labels.size(). This is so all key-value pairs in labels have an equal chance of being returned in the randomized method.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.52%. Comparing base (e62f627) to head (a0010da).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4585   +/-   ##
=======================================
  Coverage   86.52%   86.52%           
=======================================
  Files         525      525           
  Lines       20464    20464           
=======================================
  Hits        17704    17704           
  Misses       2760     2760           

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[ThomsonTan]

Could you please add an entry to the CHANGELOG.md?

[Anish701]

Could you please add an entry to the CHANGELOG.md?

Sure thing! I've updated CHANGELOG.md with this fix