Use model built label when creating labels

Author: LC43

src/Models/PostType.php

@@ -84,8 +84,8 @@ public function has_meta(): bool {
 	 */
 	protected function get_default_labels(): array {
 
-		$many_lower = strtolower( $this->many );
-		$one_lower  = strtolower( $this->one );
+		$many_lower = $this->many_low;
+		$one_lower  = $this->one_low;
 
 		$labels = [
 			'name'                  => $this->many,