remove private class from the message

Bug: 36069458
Test: n/a
Change-Id: I37cc0c64ce7c58b93971a19401827727860bc4b5
diff --git a/lifecycle/extensions/src/main/java/android/arch/lifecycle/LiveData.java b/lifecycle/extensions/src/main/java/android/arch/lifecycle/LiveData.java
index a06a300..d689442 100644
--- a/lifecycle/extensions/src/main/java/android/arch/lifecycle/LiveData.java
+++ b/lifecycle/extensions/src/main/java/android/arch/lifecycle/LiveData.java
@@ -407,8 +407,7 @@
     private void assertMainThread(String methodName) {
         if (!AppToolkitTaskExecutor.getInstance().isMainThread()) {
             throw new IllegalStateException("Cannot invoke " + methodName + " on a background"
-                    + " thread. You can easily move the call to main thread using"
-                    + " AppToolkitTaskExecutor.");
+                    + " thread");
         }
     }
 }