chore: update quickstart android project files

examples/flutter/quickstart/android/.gitignore

@@ -7,7 +7,7 @@ gradle-wrapper.jar
 GeneratedPluginRegistrant.java
 
 # Remember to never publicly share your keystore.
-# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+# See https://flutter.dev/to/reference-keystore
 key.properties
 **/*.keystore
 **/*.jks