rename ConformanceClasses to Conformance

[vincentsarago]

ref https://github.com/stac-utils/stac-fastapi/pull/625/files#diff-57e8b237e9da3926a1dcf4e137fb2dd7250ee0b2e3469a65b97d453902bff844R22-R26

cc @thomas-maschler

[vincentsarago]

FYI: Tests are failing for something unrelated to this PR I think

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (main@f0b06cc). Click here to learn what that means.

Files	Patch %	Lines
stac_pydantic/api/__init__.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #136   +/-   ##
=======================================
  Coverage        ?   96.59%           
=======================================
  Files           ?       25           
  Lines           ?      587           
  Branches        ?        0           
=======================================
  Hits            ?      567           
  Misses          ?       20           
  Partials        ?        0           

Flag	Coverage Δ
unittests	96.59% <88.88%> (?)

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