Remove test dependency mypy-extensions (pylint-dev#4969)

requirements_test_min.txt

@@ -2,4 +2,3 @@
 astroid==2.7.3  # Pinned to a specific version for tests
 pytest~=6.2
 pytest-benchmark~=3.4
-mypy_extensions==0.4.3

tests/lint/test_pylinter.py

@@ -1,14 +1,19 @@
+import sys
 from typing import Any
 from unittest.mock import patch
 
 from _pytest.capture import CaptureFixture
 from astroid import AstroidBuildingError
-from mypy_extensions import NoReturn
 from py._path.local import LocalPath  # type: ignore
 
 from pylint.lint.pylinter import PyLinter
 from pylint.utils import FileState
 
+if sys.version_info >= (3, 6, 2):
+    from typing import NoReturn
+else:
+    from typing_extensions import NoReturn
+
 
 def raise_exception(*args: Any, **kwargs: Any) -> NoReturn:
     raise AstroidBuildingError(modname="spam")