Mark web_long_running_tests_2_5 flaky (#121814)

Mark web_long_running_tests_2_5 flaky

Author: goderbauer

.ci.yaml

@@ -991,6 +991,7 @@ targets:
 
   - name: Linux web_long_running_tests_2_5
     recipe: flutter/flutter_drone
+    bringup: true # Flaky: https://github.com/flutter/flutter/issues/121707
     timeout: 60
     properties:
       dependencies: >-