Mark flutter_gallery_v2_chrome_run_test and flutter_gallery_v2_web_compile_test not flaky (#55877)

dev/devicelab/manifest.yaml

@@ -826,7 +826,6 @@ tasks:
       Checks that the New Flutter Gallery runs successfully on Chrome.
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
-    flaky: true
 
   flutter_gallery_v2_web_compile_test:
     description: >
@@ -834,4 +833,3 @@ tasks:
       and the size of the compiled code.
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
-    flaky: true