repoPath for GitLab should not add git extension

Gerrit already adds .git extension to the project name when searching
for a project on disk.

Change-Id: I3b61975b59da2385a79a1e4f5a890e10108a6006
diff --git a/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/GitBackend.java b/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/GitBackend.java
index 9499f50..974c7f2 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/GitBackend.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/gitrepometrics/GitBackend.java
@@ -29,7 +29,7 @@
     public String repoPath(String projectName) {
       String sha256OfProjectName = DigestUtils.sha256Hex(projectName);
       return String.format(
-          "%s/%s/%s.git",
+          "%s/%s/%s",
           sha256OfProjectName.substring(0, 2),
           sha256OfProjectName.substring(2, 4),
           sha256OfProjectName);