chore: remove unnecessary call

subcommands/upgrade

@@ -14,7 +14,6 @@ service-upgrade-cmd() {
   declare desc="upgrade service <service> to the specified versions"
   local cmd="$PLUGIN_COMMAND_PREFIX:upgrade" argv=("$@"); [[ ${argv[0]} == "$cmd" ]] && shift 1
   declare SERVICE="$1" CLONE_FLAGS_LIST="${@:2}"
-  is_implemented_command "$cmd" || dokku_log_fail "Not yet implemented"
 
   [[ -z "$SERVICE" ]] && dokku_log_fail "Please specify a name for the service"
   verify_service_name "$SERVICE"