Remove unused getStringFromMap method

Change-Id: I0742a1f4085064f26b76ed68e6e9bf48d6906e48

src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/UpdateGitMetricsTask.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/UpdateGitMetricsTask.java b/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/UpdateGitMetricsTask.java
index 6163a42..bb885d3 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/UpdateGitMetricsTask.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/UpdateGitMetricsTask.java
@@ -24,7 +24,6 @@
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.stream.Collectors;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.internal.storage.file.FileRepository;
 import org.eclipse.jgit.lib.Repository;
@@ -90,12 +89,6 @@
     }
   }
 
-  String getStringFromMap(Map<String, Long> m) {
-    return m.keySet().stream()
-        .map(key -> key + "=" + m.get(key))
-        .collect(Collectors.joining(", ", "{", "}"));
-  }
-
   @Override
   public String toString() {
     return "UpdateGitMetricsTask " + projectName;