Remove unconditionally skipped test (fails if skip removed)

The test was introduced in f999060 (May
2017) and was unconditionally skipped in
6cf5d7d. It remains skipped to this
day.

In commit bd850c0, the patched_file
method was removed/renamed. So even if the skip were removed, it would
fail on the undefined attribute.

This was caught via mypy which emits an error due to the missing method.

Author: jdufresne

news/5573eba9-07cc-462e-b9af-261568606c94.trivial.rst

@@ -4,8 +4,6 @@
 import re
 import textwrap
 
-import pytest
-
 from pip._internal.cli.status_codes import ERROR
 from pip._internal.configuration import CONFIG_BASENAME, get_configuration_files
 from tests.lib.configuration_helpers import ConfigurationMixin, kinds
@@ -17,18 +15,6 @@ def test_no_options_passed_should_error(script):
 
 
 class TestBasicLoading(ConfigurationMixin):
-    @pytest.mark.skip("Can't modify underlying file for any mode")
-    def test_reads_file_appropriately(self, script):
-        contents = """
-            [test]
-            hello = 1
-        """
-
-        with self.patched_file(kinds.USER, contents):
-            result = script.pip("config", "list")
-
-        assert "test.hello=1" in result.stdout
-
     def test_basic_modification_pipeline(self, script):
         script.pip("config", "get", "test.blah", expect_error=True)
         script.pip("config", "set", "test.blah", "1")