Remove unused imports after rebase

Author: dimitris-athanasiou

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/dataframe/analyses/RegressionTests.java

@@ -19,7 +19,6 @@
 import java.util.Collections;
 import java.util.Map;
 
-import static org.hamcrest.Matchers.anEmptyMap;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;