Update Travis to latest stable version.
diff --git a/.travis.yml b/.travis.yml
index 1785982..ad6ca45 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: dart
 
 dart:
-  - 2.7.0
+  - 2.10.0
   - dev
 
 dart_task: