Make migrations faster to skip if they've already been run

migrations/1752981883.sh

@@ -1,6 +1,6 @@
 echo "Replace wofi with walker as the default launcher"
 
-if [[ ! -d ~/.config/walker ]]; then
+if ! command -v walker &>/dev/null; then
   yay -Sy --noconfirm --needed walker-bin libqalculate
 
   yay -Rns --noconfirm wofi