rm unused import

Closes #1335

Author: alb-i986

src/main/java/org/junit/rules/ExternalResource.java

@@ -1,7 +1,6 @@
 package org.junit.rules;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
 import org.junit.runner.Description;