Rely on backports.entry_points_selectable for forward compatibility with importlib.metadata.

tests/integration/test_checker.py

@@ -3,7 +3,6 @@ import mock
 import pytest
 
 from flake8 import checker
-from flake8._compat import importlib_metadata
 from flake8.plugins import manager
 from flake8.processor import FileProcessor
 
@@ -104,9 +103,9 @@ def mock_file_checker_with_plugin(plugin_target):
 
     # Load the checker plugins using the entry point mock
     with mock.patch.object(
-            importlib_metadata,
+            manager,
             'entry_points',
-            return_value={'flake8.extension': [entry_point]},
+            return_value=[entry_point],
     ):
         checks = manager.Checkers()