Mark Linux Web Engine Bringup. (flutter#37658)

This is to open the tree while downloading firefox is fixed.

Bug: flutter#115404

Author: godofredoc

.ci.yaml

@@ -264,6 +264,7 @@ targets:
 
   - name: Linux Web Engine
     recipe: engine/web_engine
+    bringup: true
     properties:
       add_recipes_cq: "true"
       cores: "32"