Replace deprecated Mockito matcher import

Author: 8Keep

jme3-core/src/test/java/com/jme3/material/plugins/J3MLoaderTest.java

@@ -19,7 +19,7 @@
 import org.mockito.Mockito;
 import org.mockito.junit.MockitoJUnitRunner;
 
-import static org.mockito.Matchers.any;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.verify;
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.when;