chore: ublue-update script cleanup

system_files/desktop/shared/usr/etc/ublue-update.d/user/20-brew-update.sh

@@ -1,6 +0,0 @@
-#!/usr/bin/bash
-
-if command -v brew; then
-	brew update
-	brew upgrade
-fi

system_files/desktop/shared/usr/etc/ublue-update.d/user/99-bazzite-arch-user-update.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/bash
+#!/usr/bin/env bash
 
 if [[ $(podman ps -a --no-trunc --format {{.Names}} | grep -E '(^|\s)bazzite-arch($|\s)') ]]; then
 	unset SUDO_USER # avoid distrobox sudo checks

system_files/desktop/silverblue/usr/etc/ublue-update.d/user/80-adwaita-for-steam-user-update.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/bash
+#!/usr/bin/env bash
 shopt -s nullglob
 
 if [ -d "$HOME/homebrew/themes/Adwaita-for-Steam" ]; then

system_files/desktop/silverblue/usr/etc/ublue-update.d/user/90-mozilla-gnome-themes-user-update.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/bash
+#!/usr/bin/env bash
 shopt -s nullglob
 
 # Flatpak Firefox