Update location of intl package. (#12644)

Also switched to relative paths for local packages.

examples/flutter_gallery/BUILD.gn

diff --git a/examples/flutter_gallery/BUILD.gn b/examples/flutter_gallery/BUILD.gn
index 20b4fc8..fdece78 100644
--- a/examples/flutter_gallery/BUILD.gn
+++ b/examples/flutter_gallery/BUILD.gn
@@ -12,7 +12,7 @@
   disable_analysis = true
 
   deps = [
-    "//lib/flutter/packages/flutter",
+    "../../packages/flutter",
     "//third_party/dart-pkg/pub/url_launcher",
   ]