fix(sxmo): simplify sxmo_timezonechange.sh to always use the Alpine flow

SXMO_OS is always bananarchy (an Alpine derivative) on this device, so
the SXMO_OS case, the change_systemd branch, and the nixos branch were
dead code. Drop them and always run the Alpine flow
(doas setup-timezone -z), which is what bananarchy uses.

overlay/rootfs/usr/bin/sxmo_timezonechange.sh

@@ -15,15 +15,6 @@ change_alpine() {
 	echo "Timezone changed ok"
 }
 
-change_systemd() {
-	echo "Changing timezone to $1"
-
-	timedatectl set-timezone "$1"
-	sxmo_hook_statusbar.sh time
-
-	echo "Timezone changed ok"
-}
-
 menu() {
 	zoneinfo_dir=$(xdg_data_path zoneinfo)
 	T="$(
@@ -39,12 +30,7 @@ if [ $# -gt 0 ]; then
 	trap "read -r" EXIT
 	set -e
 
-	case "$SXMO_OS" in
+	change_alpine "$@"
-		alpine|postmarketos|bananarchy) change_alpine "$@";;
-		arch|archarm|debian) change_systemd "$@";;
-		nixos) echo "Change the timezone in configuration.nix with time.timeZone = \"[timezone]\"";;
-		*) echo "Changing the timezone isn't implemented on your distro yet";;
-	esac
 else
 	menu
 fi