Fix mypy typing for utilities.cloud_io.py

[stancld]

What does this PR do?

Part of #7037. This PR disentangles large #7218. It fixes mypy typing in utilities.cloud_io.py.

Does your PR introduce any breaking changes? If yes, please list them.

None

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[codecov]

Codecov Report

Merging #8671 (360bd71) into master (d83dd79) will decrease coverage by 4%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #8671    +/-   ##
=======================================
- Coverage      93%     89%    -4%     
=======================================
  Files         167     167            
  Lines       13954   13954            
=======================================
- Hits        12921   12381   -540     
- Misses       1033    1573   +540