Scope sticky-comment lookup to github-actions[bot]

The upsert predicate matched any bot, so a comment from a different bot
that quoted the marker string would have been overwritten with the
preview table instead of the workflow's own comment.

:house: Remote-Dev: homespace

Author: localden

.github/workflows/docs-preview.yml

@@ -194,7 +194,7 @@ jobs:
 
             async function upsert(body) {
               const comments = await github.paginate(github.rest.issues.listComments, { owner, repo, issue_number, per_page: 100 });
-              const existing = comments.find(c => c.user?.type === 'Bot' && c.body?.includes(marker));
+              const existing = comments.find(c => c.user?.login === 'github-actions[bot]' && c.body?.includes(marker));
               if (existing) {
                 await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body });
               } else {