Mark android_sample_catalog_generator as flaky (flutter#14799)

tvolkert · web-flow · commit 50b7fad6a3ec · 2018-02-20T22:14:33.000-08:00
flutter#14798
diff --git a/dev/devicelab/manifest.yaml b/dev/devicelab/manifest.yaml
@@ -218,6 +218,7 @@ tasks:
       Builds sample catalog markdown pages and Android screenshots
     stage: devicelab
     required_agent_capabilities: ["mac/android"]
+    flaky: true
 
   complex_layout_semantics_perf:
     description: >
