[flutter_gallery] Remove from topaz/packages/examples/all temporarily

This is the last remaining use of the 'persistent-storage' feature
(which is deprecated) and is blocking deletion of it.
https://github.com/flutter/flutter/pull/28193 is in progress to update
flutter_gallery.cmx. Until that rolls in, stop building flutter_gallery.

CF-28 #progress

Change-Id: I0e2edd99aa54b77245ecdd06ccb61d5b273245df
diff --git a/packages/examples/all b/packages/examples/all
index 302e0cd..2955fee 100644
--- a/packages/examples/all
+++ b/packages/examples/all
@@ -3,7 +3,6 @@
         "topaz/packages/examples/dart",
         "topaz/packages/examples/dart_sdk",
         "topaz/packages/examples/fidl",
-        "topaz/packages/examples/flutter_gallery",
         "topaz/packages/examples/misc",
         "topaz/packages/examples/modular",
         "topaz/packages/examples/mondrian",
diff --git a/packages/examples/flutter_gallery b/packages/examples/disabled/flutter_gallery
similarity index 100%
rename from packages/examples/flutter_gallery
rename to packages/examples/disabled/flutter_gallery