TC_TCCM_1_2.py: Remove disallowed attribuzte checks (project-chip#38377)

The TCCM cluster have OnMode and StartupMode attributes as disallowed by specs and also testplans have removed checking for them (see https://github.com/CHIP-Specifications/chip-test-plans/blob/master/src/cluster/mode_ref_tcc.adoc#2-test-case-list), so also the tests should not test for it

Author: Apollon77

src/python_testing/TC_TCCM_1_2.py

@@ -91,18 +91,6 @@ async def test_TC_TCCM_1_2(self):
         mode = self.cluster.Attributes.CurrentMode
         await self.read_and_check_mode(endpoint=endpoint, mode=mode, supported_modes=supported_modes)
 
-        self.step(4)
-        # Verify that the OnMode attribute has a valid value or null.
-        mode = self.cluster.Attributes.OnMode
-        await self.read_and_check_mode(endpoint=endpoint, mode=mode,
-                                       supported_modes=supported_modes, is_nullable=True)
-
-        self.step(5)
-        # Verify that the StartUpMode has a valid value or null
-        mode = self.cluster.Attributes.StartUpMode
-        await self.read_and_check_mode(endpoint=endpoint, mode=mode,
-                                       supported_modes=supported_modes, is_nullable=True)
-
 
 if __name__ == "__main__":
     default_matter_test_main()