Finetuning for the playground pull request preview

[carstingaxion]

Description of the Change

Follow-up for #666 to finalise the Playground pull request previews.

How to test the Change

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Changelog Entry

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Credits

Props @carstingaxion

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[what-the-diff]

PR Summary

• Link Redirection Change
  The code has been updated to change the address (url) through which certain services of the application are accessed. Originally, these were accessed through https://hub.carsten-bach.de/gatherpress/plugin-proxy.php, but now they will be accessed through https://gatherpress.org/playground-preview/plugin-proxy.php.

• Configuration File Adjustment
  A line in the playground-preview.yml configuration file has been removed. This line previously gave instructions to the system about the path to certain resources during development, and it was not required for the final version of the app. Consequently, it has been removed to ensure the smooth functioning of the software.

[carstingaxion]

I guess we need to adjust some repo settings to make this work.

This is, how my https://github.com/carstingaxion/gatherpress/settings/actions looks like: