Remove --use-pep517 option test

This option is now always on, so need to test it.

tests/unit/test_options.py

@@ -198,64 +198,6 @@ def test_cache_dir__PIP_NO_CACHE_DIR_invalid__with_no_cache_dir(
             main(["--no-cache-dir", "fake"])
 
 
-class TestUsePEP517Options:
-    """
-    Test options related to using --use-pep517.
-    """
-
-    def parse_args(self, args: list[str]) -> Values:
-        # We use DownloadCommand since that is one of the few Command
-        # classes with the use_pep517 options.
-        command = create_command("download")
-        options, args = command.parse_args(args)
-
-        return options
-
-    def test_no_option(self) -> None:
-        """
-        Test passing no option.
-        """
-        options = self.parse_args([])
-        assert options.use_pep517 is None
-
-    def test_use_pep517(self) -> None:
-        """
-        Test passing --use-pep517.
-        """
-        options = self.parse_args(["--use-pep517"])
-        assert options.use_pep517 is True
-
-    def test_PIP_USE_PEP517_true(self, monkeypatch: pytest.MonkeyPatch) -> None:
-        """
-        Test setting PIP_USE_PEP517 to "true".
-        """
-        monkeypatch.setenv("PIP_USE_PEP517", "true")
-        options = self.parse_args([])
-        # This is an int rather than a boolean because strtobool() in pip's
-        # configuration code returns an int.
-        assert options.use_pep517 == 1
-
-    def test_PIP_USE_PEP517_false(self, monkeypatch: pytest.MonkeyPatch) -> None:
-        """
-        Test setting PIP_USE_PEP517 to "false".
-        """
-        monkeypatch.setenv("PIP_USE_PEP517", "false")
-        options = self.parse_args([])
-        # This is an int rather than a boolean because strtobool() in pip's
-        # configuration code returns an int.
-        assert options.use_pep517 == 0
-
-    def test_use_pep517_and_PIP_USE_PEP517_false(
-        self, monkeypatch: pytest.MonkeyPatch
-    ) -> None:
-        """
-        Test passing --use-pep517 and setting PIP_USE_PEP517 to "false".
-        """
-        monkeypatch.setenv("PIP_USE_PEP517", "false")
-        options = self.parse_args(["--use-pep517"])
-        assert options.use_pep517 is True
-
-
 class TestOptionsInterspersed(AddFakeCommandMixin):
     def test_general_option_after_subcommand(self) -> None:
         # FakeCommand intentionally returns the wrong type.