Skip test_trap_config_save_after_reboot for 202012 branch (sonic-net#7373)

What is the motivation for this PR?
test_trap_config_save_after_reboot case should skipped in 202012 branch, since always_enable feature is not merged into 202012 image.
[CoPP] Add always_enabled field to coppmgr logic by noaOrMlnx · Pull Request sonic-net#2034 · sonic-net/sonic-swss (github.com)

Test case was added in this PR:
sonic-net#4891

xfail in this PR
[test] skip/xfail unmerged copp feature temporarily by yejianquan · Pull Request sonic-net#5148 · sonic-net/sonic-mgmt (github.com)

How did you do it?
Xfail is not correct, it needs to be skipped for now.
Change xfail to skip.
Signed-off-by: Zhaohui Sun <[email protected]>

Author: ZhaohuiS

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -153,7 +153,7 @@ copp/test_copp.py:
       - "topo_name not in ['ptf32', 'ptf64', 't0', 't0-64', 't0-52', 't0-116', 't1', 't1-lag', 't1-64-lag', 't1-backend', 't2', 'm0', 'mx']"
 
 copp/test_copp.py::TestCOPP::test_trap_config_save_after_reboot:
-  xfail:
+  skip:
     reason: "'Add always_enabled field to coppmgr' is not merged into 202012 yet"
     conditions:
       - "release in ['202012']"