Update the S3 client initialization to explicitly use boto3.Session()

[bhimrazy]

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

This PR updates the S3 client initialization to explicitly use boto3.Session(), ensuring proper credential refresh, especially when using temporary AWS credentials. This prevents potential ExpiredToken errors when credentials expire.

Fixes #458.

PR review

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 78%. Comparing base (a147df6) to head (8b8588f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #461   +/-   ##
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- Coverage    78%    78%   -0%     
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  Files        37     37           
  Lines      5365   5367    +2     
===================================
+ Hits       4182   4183    +1     
- Misses     1183   1184    +1