Xfail test_ecn_config_updates due to GCU changes for 202511 and master (#22334)

* Xfail test_ecn_config_updates due to GCU changes for 202511 and master

Following changes done to the GCU validator code in
sonic-net/sonic-utilities#4219, `test_ecn_config_updates` now fails with
an error saying that the config it is trying to apply should've been
rejected, but is actually applied. According to the author of the
change, the test code will be modified based on this change.

For the purposes of unblocking submodule updates of sonic-utilities on
master and 202511, xfail this test case on those two branches.

Signed-off-by: Saikrishna Arcot <[email protected]>

Author: saiarcot895

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -2471,6 +2471,11 @@ generic_config_updater/test_ecn_config_update.py::test_ecn_config_updates:
       - "topo_type in ['m0', 'mx', 'm1']"
       - "release in ['202211']"
       - "https://github.com/sonic-net/sonic-buildimage/issues/22295 and platform in ['x86_64-nvidia_sn5600-r0', 'x86_64-nvidia_sn5640-r0']"
+  xfail:
+    reason: "This test will be reworked following changes to GCU validators"
+    conditions_logical_operator: "OR"
+    conditions:
+      - "release in ['master', '202511'] and https://github.com/sonic-net/sonic-mgmt/issues/22333"
 
 generic_config_updater/test_eth_interface.py::test_replace_fec:
   skip: