refactor: Renamed all templates to end in .jinja to resolve issues with latest mypy.

[dbanty]

No description provided.

[codecov]

Codecov Report

Merging #320 (b015675) into main (cf2b002) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #320   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           47        47           
  Lines         1385      1385           
=========================================
  Hits          1385      1385           

Impacted Files	Coverage Δ
openapi_python_client/__init__.py	100.00% <100.00%> (ø)
...penapi_python_client/parser/properties/__init__.py	100.00% <100.00%> (ø)
...i_python_client/parser/properties/enum_property.py	100.00% <100.00%> (ø)
..._python_client/parser/properties/model_property.py	100.00% <100.00%> (ø)

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