chore: roll Dart rev

Author: eseidel

DEPS

@@ -20,7 +20,7 @@ vars = {
   'ocmock_git': 'https://github.com/erikdoe/ocmock.git',
   'skia_revision': '5046d9fc1551e025263a21eb0bb9f0b63569600e',
 
-  'dart_sdk_revision': '646b11a7b8f2849bebd1b5e3e6de03fb0773906d',
+  'dart_sdk_revision': 'd647d61b37286fe4184dca3f39166093c544ae55',
   'dart_sdk_git': '[email protected]:shorebirdtech/dart-sdk.git',
   'updater_git': 'https://github.com/shorebirdtech/updater.git',
   'updater_rev': 'd785568094c176d956ccf7ae918bf8d64c0d09b7',