Remove postgresflex (#74)

Co-authored-by: Henrique Santos <henrique.santos@freiheit.com>

Author: hcsa73

docs/stackit.md

@@ -34,7 +34,6 @@ stackit [flags]
 * [stackit mongodbflex](./stackit_mongodbflex.md)	 - Provides functionality for MongoDB Flex
 * [stackit opensearch](./stackit_opensearch.md)	 - Provides functionality for OpenSearch
 * [stackit organization](./stackit_organization.md)	 - Provides functionality regarding organizations
-* [stackit postgresflex](./stackit_postgresflex.md)	 - Provides functionality for PostgreSQL Flex
 * [stackit project](./stackit_project.md)	 - Provides functionality regarding projects
 * [stackit rabbitmq](./stackit_rabbitmq.md)	 - Provides functionality for RabbitMQ
 * [stackit redis](./stackit_redis.md)	 - Provides functionality for Redis