build: ensure action: merge label is included on release PRs (#40016)

The release PRs should include the `action: merge`, `PullApprove: disable` and `comp: build & ci`
labels.

PR Close #40016

.ng-dev/release.ts

@@ -32,4 +32,7 @@ export const release: ReleaseConfig = {
   generateReleaseNotesForHead: async () => {
     exec('yarn -s gulp changelog', {cwd: join(__dirname, '../')});
   },
+  // The `comp: *` labels will be automatically added by PullApprove and the targeting label will
+  // be added by the release tooling, only `action: merge` must be manually included to the list.
+  releasePrLabels: ['comp: build & ci', 'action: merge', 'PullApprove: disable'],
 };