Fix version syntax in test_nowarn_accidental_env_marker_misconfig

Fix the two "marker"-alike cases (for package `python_version`)
for test_nowarn_accidental_env_marker_misconfig to use `<3` rather
than `<'3'`.  The latter maps to the version `'3'` which is not a valid
version and therefore causes an error with packaging-22.0+.

See the discussion at
506e7e7#r97577660

Author: mgorny

setuptools/tests/config/test_setupcfg.py

@@ -746,12 +746,12 @@ def test_warn_accidental_env_marker_misconfig(self, config, tmpdir):
             "[options.extras_require]\nfoo = bar;baz\nboo = xxx;yyy",
             "[options.extras_require]\nfoo =\n    bar;python_version<'3'\n",
             "[options.extras_require]\nfoo = bar;baz\nboo = xxx;yyy\n",
-            "[options.extras_require]\nfoo =\n    bar\n    python_version<'3'\n",
+            "[options.extras_require]\nfoo =\n    bar\n    python_version<3\n",
             "[options]\ninstall_requires =\n    bar;python_version<'3'",
             "[options]\ninstall_requires = bar;baz\nboo = xxx;yyy",
             "[options]\ninstall_requires =\n    bar;python_version<'3'\n",
             "[options]\ninstall_requires = bar;baz\nboo = xxx;yyy\n",
-            "[options]\ninstall_requires =\n    bar\n    python_version<'3'\n",
+            "[options]\ninstall_requires =\n    bar\n    python_version<3\n",
         ],
     )
     def test_nowarn_accidental_env_marker_misconfig(self, config, tmpdir, recwarn):