Delete old test case

Author: barneygale

Lib/test/test_pathlib/test_pathlib_abc.py

@@ -336,10 +336,6 @@ def test_glob_windows(self):
 class WritablePathTest(JoinablePathTest):
     cls = DummyWritablePath
 
-    def test_is_writable(self):
-        p = self.cls(self.base)
-        self.assertIsInstance(p, _WritablePath)
-
 
 class DummyRWPath(DummyWritablePath, DummyReadablePath):
     __slots__ = ()