Remove bringup: true from web tests. (#160788)

We should make this a blocking CI step ASAP.

Author: eyebrowsoffire

engine/src/flutter/.ci.yaml

@@ -399,7 +399,6 @@ targets:
       cores: "8"
 
   - name: Linux linux_web_engine_tests
-    bringup: true
     recipe: engine_v2/engine_v2
     timeout: 120
     properties: