Add __contains__ in dict_items

Lib/test/test_dict.py

@@ -1300,8 +1300,6 @@ class DictTest(unittest.TestCase):
         except RuntimeError:  # implementation defined
             pass
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_dictitems_contains_use_after_free(self):
         class X:
             def __eq__(self, other):

vm/src/builtins/dict.rs

@@ -997,7 +997,7 @@ impl PyDictItems {
         }
         let key = needle.fast_getitem(0);
         let found = zelf.dict().contains(key.clone(), vm)?;
-        if found == false {
+        if !found {
             return Ok(false);
         }
         let value = needle.fast_getitem(1);