MediaRouter: Fixes a build error

add missing import to fix build error

Bug: 149367764
Test: atest android.media.cts.MediaRouter2Test
Change-Id: I4f361a942330a0f23df35d71f3a9ea09f4143158
diff --git a/tests/tests/media/src/android/media/cts/MediaRouter2Test.java b/tests/tests/media/src/android/media/cts/MediaRouter2Test.java
index 0697005..421402f 100644
--- a/tests/tests/media/src/android/media/cts/MediaRouter2Test.java
+++ b/tests/tests/media/src/android/media/cts/MediaRouter2Test.java
@@ -55,6 +55,7 @@
 import org.junit.runner.RunWith;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;