patchsend-pack: unify error messages for unsupported capabilities

> If --signed is not supported, the error message names the remote
> "receiving end". If --atomic is not supported, the error message
> names the remote "server". Unify the naming to "receiving end"
> as we're in the context of "push".
>
> Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
> ---

>  send-pack.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/send-pack.c b/send-pack.c
> index 9d2b0c5..189bdde 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -356,21 +356,21 @@ int send_pack(struct send_pack_args *args,
>  			die(_("the receiving end does not support --signed push"));
>  		push_cert_nonce = xmemdupz(push_cert_nonce, len);
>  	}
>  
>  	if (!remote_refs) {
>  		fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
>  			"Perhaps you should specify a branch such as 'master'.\n");
>  		return 0;
>  	}
>  	if (args->atomic && !atomic_supported)
> -		die(_("server does not support --atomic push"));
> +		die(_("the receiving end does not support --atomic push"));
>  
>  	use_atomic = atomic_supported && args->atomic;
>  
>  	if (status_report)
>  		strbuf_addstr(&cap_buf, " report-status");
>  	if (use_sideband)
>  		strbuf_addstr(&cap_buf, " side-band-64k");
>  	if (quiet_supported && (args->quiet || !args->progress))
>  		strbuf_addstr(&cap_buf, " quiet");
>  	if (use_atomic)