Use consistent bash5 style for conditionals and quoting

bin/omarchy-update-available

@@ -2,19 +2,19 @@
 
 # Get remote tag
 latest_tag=$(git -C "$OMARCHY_PATH" ls-remote --tags origin | grep -v "{}" | awk '{print $2}' | sed 's#refs/tags/##' | sort -V | tail -n 1)
-if [[ -z "$latest_tag" ]]; then
+if [[ -z $latest_tag ]]; then
   echo "Error: Could not retrieve latest tag."
   exit 1
 fi
 
 # Get local tag
 current_tag=$(git -C "$OMARCHY_PATH" describe --tags $(git -C "$OMARCHY_PATH" rev-list --tags --max-count=1))
-if [[ -z "$current_tag" ]]; then
+if [[ -z $current_tag ]]; then
   echo "Error: Could not retrieve current tag."
   exit 1
 fi
 
-if [[ "$current_tag" != "$latest_tag" ]]; then
+if [[ $current_tag != $latest_tag ]]; then
   echo "Omarchy update available ($latest_tag)"
   exit 0
 else