Removed unused import from RequiredPipelineIT.java

This commit removes an unused import that was left behind after cleaning
up a backport. Sorry.

Author: jasontedor

server/src/test/java/org/elasticsearch/index/RequiredPipelineIT.java

@@ -25,7 +25,6 @@
 
 import java.io.IOException;
 import java.util.Collections;
-import java.util.Map;
 
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.hasToString;