Fix instructions for running test

Test: atest CtsWindowManagerDeviceTestCases:MultiDisplayClientTests :D
Change-Id: I4cd817841559a2dbea571c2e7921999090a91390
diff --git a/tests/framework/base/windowmanager/src/android/server/wm/MultiDisplayClientTests.java b/tests/framework/base/windowmanager/src/android/server/wm/MultiDisplayClientTests.java
index 6d204a4..c055950 100755
--- a/tests/framework/base/windowmanager/src/android/server/wm/MultiDisplayClientTests.java
+++ b/tests/framework/base/windowmanager/src/android/server/wm/MultiDisplayClientTests.java
@@ -61,7 +61,7 @@
 
 /**
  * Build/Install/Run:
- *     atest CtsActivityManagerDeviceTestCases:MultiDisplayClientTests
+ *     atest CtsWindowManagerDeviceTestCases:MultiDisplayClientTests
  */
 @Presubmit
 @MediumTest