mirrors: update rsync-ssl instructions for updates Arch script

Upstream included TLS support and enables it by default now:
https://gitlab.archlinux.org/archlinux/infrastructure/-/merge_requests/1022

Author: lazka

web/dev/mirrors.md

@@ -97,8 +97,7 @@ source_url='rsync://repo.msys2.org/builds/'
 lastupdate_url='https://repo.msys2.org/lastupdate'
 ```
 
-Since our server has TLS/SSL support, you can replace the `rsync` command in the
-script with `rsync-ssl`.
+Our rsync server has TLS/SSL support, so keep `tls=1` as is.
 
 To register your mirror please open an issue here:
 https://github.com/msys2/msys2.github.io/issues