chore: handle push of unchanged schema

ctl/SubGraphs.graphql

@@ -1,9 +1,13 @@
 query SubGraphs($ref: String!) {
-  subGraphs(ref: $ref) {
-    service
-    url
-    wsUrl
-    changedBy
-    changedAt
+  supergraph(ref: $ref) {
+    ... on SubGraphs {
+      subGraphs {
+        service
+        url
+        wsUrl
+        changedBy
+        changedAt
+      }
+    }
   }
 }