Fix flaky configlet-sync job (#443)

The job sometimes fails because we're hitting a rate limit.
Removing `update_existing: true` seems to the main culprit
for hitting the rate limit.

See JasonEtco/create-an-issue#142 (comment)

works on #359

Author: fapdash

.github/workflows/configlet-sync.yml

@@ -39,4 +39,3 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           filename: .github/configlet-sync-issue.md
-          update_existing: true