Replace deprecated Mockito-class

core/src/test/java/com/threerings/getdown/data/PathBuilderTest.java

@@ -7,7 +7,6 @@ package com.threerings.getdown.data;
 
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Path;
 import java.util.Arrays;
 
 import org.junit.*;
@@ -16,7 +15,7 @@ import org.junit.runner.RunWith;
 import static org.junit.Assert.assertEquals;
 
 import org.mockito.Mock;
-import org.mockito.runners.MockitoJUnitRunner;
+import org.mockito.junit.MockitoJUnitRunner;
 import static org.mockito.Mockito.when;
 
 @RunWith(MockitoJUnitRunner.class)