pycompat: drop test involving assigning "foo" to `sys.hexversion`

Starting with python 3.13, `sys.hexversion` refuse to be assigned non-hex value
like "foo". I don't think I can blame it. It is time to drop that part of the
tests.

tests/test-parseindex2.py

@@ -221,7 +221,6 b' class parseindex2tests(unittest.TestCase'
         # Test different major-minor versions.
         self.assertversionfail(3, makehex(major + 1, minor, micro))
         self.assertversionfail(4, makehex(major, minor + 1, micro))
-        self.assertversionfail(5, "'foo'")
 
     def testbadargs(self):
         # Check that parse_index2() raises TypeError on bad arguments.