fix(ci): remove --fail from curl in poll-upstream version check

--fail causes curl to exit 22 on HTTP errors before --write-out can
capture the response code, breaking the 200/404 branching logic.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/poll-upstream.yml

@@ -26,7 +26,6 @@ jobs:
           # Strip leading 'v' because RPM versions don't use it.
           version="${UPSTREAM_TAG#v}"
           http_response_code=$(curl \
-              --fail \
               --silent \
               --write-out "%{http_code}" \
               --output /dev/null \