update sdk contraint for 2.11 (#26)

* update sdk contraint for 2.11
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0ffdb0..0997a12 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+### 3.0.0-nullsafety.2
+
+* Update supported SDK range.
+
 ### 3.0.0-nullsafety.1
 
 * Migrate package to null-safe dart.
diff --git a/pubspec.yaml b/pubspec.yaml
index 0cc5ec6..1f761a5 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: platform
-version: 3.0.0-nullsafety.1
+version: 3.0.0-nullsafety.2
 description: A pluggable, mockable platform abstraction for Dart.
 homepage: https://github.com/google/platform.dart
 
@@ -7,4 +7,4 @@
   test: ^1.16.0-nullsafety.1
 
 environment:
-  sdk: '>=2.10.0-4.0.dev <2.10.0'
+  sdk: '>=2.10.0-0.0 <2.11.0'