Don't format version to 5 characters in new version message

Change-Id: I6c734170173f77a6fef0678f189e198bdaeec425
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254668
Tested-by: David Pursehouse <dpursehouse@collab.net>
Reviewed-by: Mike Frysinger <vapier@google.com>

main.py

@@ -295,7 +295,7 @@ repo: error:
 
   if exp > ver:
     print("""
-... A new version of repo (%5s) is available.
+... A new version of repo (%s) is available.
 ... You should upgrade soon:
 
     cp %s %s