Update psalm settings

Deprecation: Psalm stubs for ext-apcu loaded using legacy way. Instead, please declare ext-apcu as dependency in composer.json or use and/or directives in Psalm config.

-> maybe we don't need apcu, so we can remove it from the docker file. @BacLuc read that this was replaced with opcache in php 7.

Deprecation: Psalm stubs for ext-redis loaded using legacy way. Instead, please declare ext-redis as dependency in composer.json or use and/or directives in Psalm config.