Track MimeMap moving to libcore.content.type.

Another CL in this topic moves libcore.net.MimeMap to package
libcore.content.type. This CL updates associated references.

Bug: 136256059
Bug: 124232146
Test: Treehugger
Test: CtsMimeMapTestCases
Change-Id: I60fceae7b0d1ed00896e8f3796616d6c89bb244f
diff --git a/tests/common/com/android/documentsui/testing/TestModel.java b/tests/common/com/android/documentsui/testing/TestModel.java
index 2f2eec2..7df7b27 100644
--- a/tests/common/com/android/documentsui/testing/TestModel.java
+++ b/tests/common/com/android/documentsui/testing/TestModel.java
@@ -27,7 +27,7 @@
 import com.android.documentsui.base.Features;
 import com.android.documentsui.roots.RootCursorWrapper;
 
-import libcore.net.MimeMap;
+import libcore.content.type.MimeMap;
 
 import java.util.Random;