Change to use same syntax as check for composer

There's a proposed solution to #4247 (which doesn't seem to have been committed - I'll fix that in a moment). I've changed the test I'm using to match that suggestion.

ct/kimai.sh

@@ -23,7 +23,7 @@ function update_script() {
   header_info
   check_container_storage
   check_container_resources
-  if [[ ! -x /bin/lsb_release]]; then
+  if ! command -v lsb_release; then
     apt install -y lsb-release
   fi
   if [[ ! -d /opt/kimai ]]; then