fix: add updated_at to graphql query (#5611)

packages/netlify-cms-backend-github/src/GraphQLAPI.ts

@@ -66,6 +66,7 @@ type GraphQLPullRequest = {
   state: string;
   title: string;
   mergedAt: string | null;
+  updatedAt: string | null;
   labels: { nodes: { name: string }[] };
   repository: {
     id: string;

packages/netlify-cms-backend-github/src/fragments.ts

@@ -50,6 +50,7 @@ export const pullRequest = gql`
     state
     title
     merged_at: mergedAt
+    updated_at: updatedAt
     repository {
       ...RepositoryParts
     }