ci: Drop /health from smoke test (moved behind VPN)

/health, /admin, /metrics and /sales-dashboard are now only
reachable via internal.flagsmith.com (VPN). Public preview URLs
return 404 for these paths.

Keep /config/project-overrides (Express server-side route, proves
the server is running) and / (proves static files are deployed).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: talissoncosta

.github/workflows/frontend-pull-request.yml

@@ -84,7 +84,7 @@ jobs:
             fi
 
             # Smoke test the deployment
-            for ENDPOINT in "/health" "/config/project-overrides" "/"; do
+            for ENDPOINT in "/config/project-overrides" "/"; do
               echo "🔍 Testing $URL$ENDPOINT ..."
               STATUS=$(curl -s -o /dev/null -w '%{http_code}' --max-time 30 "$URL$ENDPOINT")
               if [ "$STATUS" != "200" ]; then