Update docs

[sujuka99]

1. https://github.com/bakdata/kpops/blob/v3/docs/docs/resources/pipeline-config/config.yaml#L19-L21

- default_output_topic_name: ${pipeline.name}-${component_name}
+ default_output_topic_name: ${pipeline.name}-${component.name}
  # Configures the value for the variable ${error_topic_name}
- default_error_topic_name: ${pipeline.name}-${component_name}-error
+ default_error_topic_name: ${pipeline.name}-${component.name}-error

2. https://github.com/bakdata/kpops/blob/v3/docs/docs/user/core-concepts/variables/substitution.md?plain=1#L29-L30

-   `error_topic_name` is an alias for `topic_name_config.default_error_topic_name`  
+   `error_topic_name` is an alias for `config.topic_name_config.default_error_topic_name`  
-   `output_topic_name` is an alias for `topic_name_config.default_output_topic_name`
+   `output_topic_name` is an alias for `config.topic_name_config.default_output_topic_name`

3. https://github.com/bakdata/kpops/blob/v3/docs/docs/user/core-concepts/variables/substitution.md?plain=1#L24

Mention the prefix!