Test: remove cluster permission from CCS user (#30262)

This commit updates the multi cluster search test with security so that
the user that is simply performing a multi cluster search does not have
any cluster permissions. This is done as none are needed by this user
and excess privileges could mask a behavior change.

x-pack/qa/multi-cluster-search-security/src/test/resources/rest-api-spec/test/multi_cluster/10_basic.yml

@@ -19,7 +19,7 @@ setup:
         name: "x_cluster_role"
         body:  >
             {
-              "cluster": ["all"],
+              "cluster": [],
               "indices": [
                 {
                   "names": ["local_index", "my_remote_cluster:test_i*", "my_remote_cluster:aliased_test_index", "test_remote_cluster:test_i*", "my_remote_cluster:secure_alias"],