fix: explain pending branch automerge checkbox behavior (#10569)

lib/workers/repository/__fixtures__/master-issue_with_8_PR.txt

@@ -29,7 +29,7 @@ These updates encountered an error and will be retried. Click a checkbox below t
 
 ## Pending Branch Automerge
 
-These updates await pending status checks before automerging.
+These updates await pending status checks before automerging. Click on a checkbox to abort the branch automerge, and create a PR instead.
 
  - [ ] <!-- approvePr-branch=branchName9 -->pr9
 

lib/workers/repository/dependency-dashboard.ts

@@ -232,7 +232,7 @@ export async function ensureDependencyDashboard(
   );
   if (prPendingBranchAutomerge.length) {
     issueBody += '## Pending Branch Automerge\n\n';
-    issueBody += `These updates await pending status checks before automerging.\n\n`;
+    issueBody += `These updates await pending status checks before automerging. Click on a checkbox to abort the branch automerge, and create a PR instead.\n\n`;
     for (const branch of prPendingBranchAutomerge) {
       issueBody += getListItem(branch, 'approvePr');
     }