bug#47051: 27.1; Incorrect backward-button signature in elisp manual

[Matt Armstrong]

Howard Melman <hmelman@gmail.com> writes:

> In the Emacs 27.1 lispref manual node Button Buffer Commands:
>
> The documentation of backward-button mentions the last
> argument NO-ERROR but doesn't include it on the command
> signature.
>
> Also the last sentence of the descriptions for both
> backward-button and forward-button says:
>
>     If NO-ERROR in non-‘nil’
>
> and I think both should be:
>
>     If NO-ERROR is non-‘nil’
>
> I believe these are still problems in master.
>
> The docstrings of both commands seem fine.