Replace 'A new repo command' with 'A new version of repo'

Change-Id: I3288f5c963b69d05d113fc039e4b4f22721f1de9
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254667
Tested-by: David Pursehouse <dpursehouse@collab.net>
Reviewed-by: Mike Frysinger <vapier@google.com>

main.py

@@ -286,7 +286,7 @@ def _CheckWrapperVersion(ver_str, repo_path):
 repo: error:
 !!! Your version of repo %s is too old.
 !!! We need at least version %s.
-!!! A new repo command (%s) is available.
+!!! A new version of repo (%s) is available.
 !!! You must upgrade before you can continue:
 
     cp %s %s
@@ -295,7 +295,7 @@ repo: error:
 
   if exp > ver:
     print("""
-... A new repo command (%5s) is available.
+... A new version of repo (%5s) is available.
 ... You should upgrade soon:
 
     cp %s %s