MM-64610: Restrict import upload for shared channels feature. (#31659)

server/i18n/en.json

@@ -2878,6 +2878,10 @@
     "id": "api.remote_cluster.get.not_found",
     "translation": "Remote Cluster not found"
   },
+  {
+    "id": "api.remote_cluster.import_not_allowed.app_error",
+    "translation": "Remote cluster import is not allowed"
+  },
   {
     "id": "api.remote_cluster.invalid_id.app_error",
     "translation": "Invalid id."