fix: Add .default to azure credential provider scope URL

[nameexhaustion]

Fixes #20640

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.02%. Comparing base (2e0b3a3) to head (2cae8f3).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
py-polars/polars/io/cloud/credential_provider.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20651      +/-   ##
==========================================
- Coverage   79.02%   79.02%   -0.01%     
==========================================
  Files        1557     1557              
  Lines      220551   220551              
  Branches     2514     2514              
==========================================
- Hits       174283   174282       -1     
- Misses      45695    45696       +1     
  Partials      573      573              

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