Rev mojo_sdk

Generated via:
`./mojo/dart/tools/release/rev_sdk.py`

TBR=zra@google.com
BUG=

Review URL: https://codereview.chromium.org/1828543006 .
diff --git a/mojo/dart/packages/mojo_sdk/CHANGELOG.md b/mojo/dart/packages/mojo_sdk/CHANGELOG.md
index 22798ef..23d45e1 100644
--- a/mojo/dart/packages/mojo_sdk/CHANGELOG.md
+++ b/mojo/dart/packages/mojo_sdk/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 0.2.21
+
+  - 25 changes: https://github.com/domokit/mojo/compare/ccd4c03...b013d06
+
+  MOJO_SDK: b013d061e7904f5e8a26fe94e64481b01444886d
+
 ## 0.2.20
 
   - 58 changes: https://github.com/domokit/mojo/compare/368aeb0...68bf047
diff --git a/mojo/dart/packages/mojo_sdk/pubspec.yaml b/mojo/dart/packages/mojo_sdk/pubspec.yaml
index c7bd435..e7aa316 100644
--- a/mojo/dart/packages/mojo_sdk/pubspec.yaml
+++ b/mojo/dart/packages/mojo_sdk/pubspec.yaml
@@ -1,8 +1,8 @@
 author: Chromium Authors <mojo-dev@googlegroups.com>
 dependencies:
-  mojo: 0.4.17
-  mojo_services: 0.4.23
+  mojo: 0.4.18
+  mojo_services: 0.4.24
 description: A meta package for the Dart Mojo SDK
 homepage: https://github.com/domokit/mojo
 name: mojo_sdk
-version: 0.2.20
+version: 0.2.21