[chore][mdatagen] Fix metrics test bug with resource attributes

[crobert-1]

Description

When a test manually overrides the default value for a resource attribute, the test needs to account for warnings logged when the resource attribute is enabled.

Link to tracking issue

Fixes #15007

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.20%. Comparing base (6a56478) to head (eee6fba).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15008      +/-   ##
==========================================
- Coverage   91.22%   91.20%   -0.02%     
==========================================
  Files         697      697              
  Lines       44627    44627              
==========================================
- Hits        40710    40704       -6     
- Misses       2773     2777       +4     
- Partials     1144     1146       +2     

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