[action] Keep 'request for xxx branch' label when finished auto-cherry-pick. (#13107)

Why I did it
To keep 'Request for xxx branch' label when finished auto-cherry-pick.

How I did it
Change logic in post cherry pick action.

How to verify it

Author: liushilongbuaa

.github/workflows/pr_cherrypick_poststep.yml

@@ -46,4 +46,4 @@ jobs:
           exit 1
         fi
         gh pr edit $origin_pr_url --add-label "Included in ${base_ref} Branch"
-        gh pr edit $origin_pr_url --remove-label "Created PR to ${base_ref} Branch,Request for ${base_ref} Branch,Approved for ${base_ref} Branch"
+        gh pr edit $origin_pr_url --remove-label "Created PR to ${base_ref} Branch,Approved for ${base_ref} Branch"