Remove expectedFailure decorator

Author: harupy

Lib/test/test_ast.py

@@ -1978,8 +1978,6 @@ def test_multi_line_str(self):
         self._check_end_pos(assign, 3, 40)
         self._check_end_pos(assign.value, 3, 40)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_continued_str(self):
         s = dedent('''
             x = "first part" \\