fix(tests/NoCredentialsError): use aws_credentials fixture

[gagantrivedi]

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Changes

Remove s3 initialization from global scope

How did you test this code?

tested by removing my ~/.aws creds

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (068253e) 96.08% compared to head (95666bf) 96.08%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3131   +/-   ##
=======================================
  Coverage   96.08%   96.08%           
=======================================
  Files        1054     1054           
  Lines       31702    31708    +6     
=======================================
+ Hits        30462    30468    +6     
  Misses       1240     1240           

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