ci: reduce test timeout to 900s and remove reruns

1800s timeout + reruns caused airflow to run 3.5+ hours.
900s (15 min) is plenty for any single test. Removing reruns
since k8s deployer failures are deterministic (same workflow
fails the same way on rerun), so reruns just waste time.

Author: Nissan Pow

.github/workflows/ux-tests.yml

@@ -258,9 +258,7 @@ jobs:
             -n ${{ matrix.workers }} \
             -v \
             --tb=short \
-            --timeout=1800 \
-            --reruns 1 \
-            --reruns-delay 10 \
+            --timeout=900 \
             --cov=metaflow \
             --cov-report=term-missing \
             --cov-report=xml:coverage.xml \