fix(mypy): add type ignore comment for File class FieldInfo inheritance

Add type: ignore[misc] comment to suppress mypy error about inheriting
from final FieldInfo class in Pydantic. This matches the upstream pattern
used for similar classes and allows the code to pass mypy type checking
in Python 3.10+.

- Fix mypy error: Cannot inherit from final class 'FieldInfo'
- Matches upstream _File class pattern with type ignore
- All tests passing (25/25)
- All quality checks passing (format, lint, mypy)

Author: oyiz-michael

aws_lambda_powertools/event_handler/openapi/params.py

@@ -947,7 +947,7 @@ def __init__(
         )
 
 
-class File(Form):
+class File(Form):  # type: ignore[misc]
     """
     A class used to represent a file parameter in a path operation.
     """