[Observatory] Updated Dart icon to new colour scheme

Change-Id: I8565e23df3b6945f424b7d3979787b290dfc3d7a
Reviewed-on: https://dart-review.googlesource.com/c/70742
Auto-Submit: Ben Konyi <bkonyi@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>
diff --git a/runtime/observatory/web/favicon.ico b/runtime/observatory/web/favicon.ico
index 7ba349b..c861395 100644
--- a/runtime/observatory/web/favicon.ico
+++ b/runtime/observatory/web/favicon.ico
Binary files differ