rsvg-convert.1: Note on the environment variables used for the system language
rsvg-convert.1: Note on the environment variables used for the system language

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/547>

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg