"rover" command line snippets have line numbers instead of bash indicator

[EverlastingBugstopper]

i would expect a single CLI snippet like this to start with $ instead of 1 since it's not a source file but a terminal.

in GitHub, you can highlight terminal snippets with the "console" markdown tag. not sure if our MDX parser can handle that though.

raw markdown:

```console
$ rover graph introspect
output
output
output
\```

highlighted:

$ rover graph introspect
output
output
output