mesonpy: support Python maintenance branches

The version reported by the 3.10 CPython branch is "3.10.5+" which fails the
metadata check.

This strips any trailing '+' that may be on the end of the version string.

Signed-off-by: Filipe Laíns <lains@riseup.net>

mesonpy/__init__.py

@@ -470,7 +470,7 @@ def _validate_metadata(self) -> None:
         # check if we are running on an unsupported interpreter
         if self._metadata.requires_python:
             self._metadata.requires_python.prereleases = True
-            if platform.python_version() not in self._metadata.requires_python:
+            if platform.python_version().rstrip('+') not in self._metadata.requires_python:
                 raise MesonBuilderError(
                     f'Unsupported Python version `{platform.python_version()}`, '
                     f'expected `{self._metadata.requires_python}`'