馃崚 kcm_regionandlang: always set LC_* when changing language
If the LC_* is not set with Plasma (~/.config/plasma-localerc), they inherit system-wide setting. However, we don't take system-wide setting into account when displaying LC_* vars. As the result, the UI may display incorrect results. Always set LC_* when changing language to avoid this issue.
(cherry picked from commit 5a687105)
Co-authored-by: Han Young hanyoung@protonmail.com