remove unused imports

Author: Vladimir Kotal

opengrok-indexer/src/main/java/org/opengrok/indexer/history/GitRepository.java

@@ -25,12 +25,8 @@
 package org.opengrok.indexer.history;
 
 import java.io.File;
-import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.io.OutputStream;
-import java.io.Reader;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Paths;
 import java.util.Date;