Restrict the Mergify copy command to core contributors (backport #22789) (#22791)

* Restrict the Mergify copy command to core contributors

(cherry picked from commit c0638439be)

# Conflicts:
#	.mergify.yml

* Update .mergify.yml

Co-authored-by: Michael Vines <mvines@gmail.com>

.mergify.yml

@@ -65,20 +65,11 @@ pull_request_rules:
       backport:
         ignore_conflicts: true
         branches:
-          - v1.5
+          - v1.9
-  - name: v1.6 backport
+
+commands_restrictions:
+  # The author of copied PRs is the Mergify user.
+  # Restrict `copy` access to Core Contributors
+  copy:
     conditions:
-      - label=v1.6
+    - author=@core-contributors
-    actions:
-      backport:
-        ignore_conflicts: true
-        branches:
-          - v1.6
-  - name: v1.7 backport
-    conditions:
-      - label=v1.7
-    actions:
-      backport:
-        ignore_conflicts: true
-        branches:
-          - v1.7