chore: Remove unused locals

[l0b0]

Related Issue(s): #331

Description:

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov-commenter]

Codecov Report

Merging #519 (0b8dd59) into main (f2afd5a) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #519      +/-   ##
==========================================
- Coverage   94.25%   94.25%   -0.01%     
==========================================
  Files          71       71              
  Lines       10269    10263       -6     
  Branches     1072     1072              
==========================================
- Hits         9679     9673       -6     
  Misses        422      422              
  Partials      168      168              

Impacted Files	Coverage Δ
pystac/catalog.py	91.60% <ø> (ø)
pystac/extensions/label.py	93.67% <ø> (-0.02%)	⬇️
pystac/serialization/common_properties.py	79.62% <ø> (-0.73%)	⬇️
pystac/validation/schema_uri_map.py	75.34% <ø> (-0.98%)	⬇️
pystac/extensions/base.py	90.56% <100.00%> (ø)

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[duckontheweb]

Looks good, thanks for all the clean-up work you are doing!