docs: correct a mention about getting long vs. short help
I haven't checked, but I think `jj help git push` used to give the
short form with `clap` 2. With `clap` 3, it's definitely the long form
anyway.
@@ -5,8 +5,8 @@ repo, which means that you can collaborate with Git users without them even
knowing that you're not using the `git` CLI.
See `jj help git` for help about the `jj git` family of commands, and e.g.
-`jj help git push` for help about a specific command (use `jj git push --help`
-for more verbose help).
+`jj help git push` for help about a specific command (use `jj git push -h` for
+briefer help).
## Creating an empty repo
