Skip pfcwd_all_port_storm test on Arista-7060X6-64PE-256x200G (#14756)

Signed-off-by: Janetxxx <janet970527@gmail.com>

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -1003,6 +1003,13 @@ pfcwd/test_pfc_config.py::TestPfcConfig::test_forward_action_cfg:
      conditions:
         - "asic_type in ['cisco-8000']"
 
+pfcwd/test_pfcwd_all_port_storm.py:
+   skip:
+     reason: "Slow pfc generation rate on 7060x6 200Gb,
+              pfc generation function on the Arista fanout device need to be improved by Arista"
+     conditions:
+      - "hwsku in ['Arista-7060X6-64PE-256x200G']"
+
 pfcwd/test_pfcwd_function.py::TestPfcwdFunc::test_pfcwd_no_traffic:
    skip:
      reason: "This test is applicable only for cisco-8000"