Fix: RepoCommandLink's text is wrong

The title of the "repo download" link was mistakenly set to "checkout"
during refactoring in commit cbc629f.

Change it to the correct "repo download" title.

Bug: Issue 2093
Change-Id: I4c30d0fedf56942f741edbbfaa7505052e5e370c

gerrit-gwtui/src/main/java/com/google/gerrit/client/download/DownloadCommandLink.java

@@ -86,7 +86,7 @@ public class RepoCommandLink extends DownloadCommandLink {
       String projectName;
       String ref;
       public RepoCommandLink(String project, String ref) {
-        super(DownloadCommand.REPO_DOWNLOAD, "checkout");
+        super(DownloadCommand.REPO_DOWNLOAD, "repo download");
         this.projectName = project;
         this.ref = ref;
       }