[dhcp_relay] Skip test_dhcp_relay_restart_with_stress in vs (#16451)

What is the motivation for this PR?
Skip test_dhcp_relay_restart_with_stress in vs due to flaky issue #16450

How did you do it?
Skip in condition mark

How did you verify/test it?
Run test

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -413,6 +413,13 @@ dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_unicast_mac:
       - "'dualtor' in topo_name and release in ['201811', '201911']"
       - "platform in ['x86_64-8111_32eh_o-r0']"
 
+dhcp_relay/test_dhcp_relay_stress.py::test_dhcp_relay_restart_with_stress:
+  skip:
+    reason: "Skip due to flaky issue"
+    conditions:
+      - "asic_type in ['vs']"
+      - "https://github.com/sonic-net/sonic-mgmt/issues/16450"
+
 dhcp_relay/test_dhcp_relay_stress.py::test_dhcp_relay_stress:
   skip:
     reason: "1. Need to skip for platform armhf-nokia_ixs7215_52x-r0 due to buffer issues