Remove unused imports (#527)

Author: magicDGS

src/main/java/org/magicdgs/readtools/tools/barcodes/dictionary/BarcodeDictionary.java

@@ -30,7 +30,6 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;

src/test/java/org/magicdgs/readtools/utils/distmap/DistmapGATKWriterUnitTest.java

@@ -33,7 +33,6 @@
 import org.broadinstitute.hellbender.utils.read.GATKReadWriter;
 import org.broadinstitute.hellbender.utils.test.IntegrationTestSpec;
 import org.mockito.Mockito;
-import org.mockito.stubbing.Answer;
 import org.testng.annotations.DataProvider;
 import org.testng.annotations.Test;