refactor: Mark legacy code with YORE comment

Author: pawamoy

project/src/mkdocstrings_handlers/{{python_package_import_name}}/_internal/config.py.jinja

@@ -35,6 +35,7 @@ try:
     if getattr(pydantic, "__version__", "1.").startswith("1."):
         raise ImportError  # noqa: TRY301
 
+    # YORE: EOL 3.9: Remove block.
     if sys.version_info < (3, 10):
         try:
             import eval_type_backport  # noqa: F401