Add mypyc test marks to new tests that patch (#3871)

This is enough for me to get a clean test run on Python 3.9 with mypyc.
I have not been able to repro the pickle failures on either Linux or
macOS.

tests/test_black.py

@@ -1985,6 +1985,7 @@ def test_cache_multiple_files(self) -> None:
             assert not cache.is_changed(one)
             assert not cache.is_changed(two)
 
+    @pytest.mark.incompatible_with_mypyc
     @pytest.mark.parametrize("color", [False, True], ids=["no-color", "with-color"])
     def test_no_cache_when_writeback_diff(self, color: bool) -> None:
         mode = DEFAULT_MODE
@@ -2046,6 +2047,7 @@ def test_write_cache_read_cache(self) -> None:
             read_cache = black.Cache.read(mode)
             assert not read_cache.is_changed(src)
 
+    @pytest.mark.incompatible_with_mypyc
     def test_filter_cached(self) -> None:
         with TemporaryDirectory() as workspace:
             path = Path(workspace)