Remove LibreX (Unmaintained since June 2023)

- ref: awesome-selfhosted#1
- `ERROR:awesome_lint.py: LibreX: last updated -366 days, 1:30:55.443609 ago, older than 365 days`
- In a security issue, a contributor mentioned that LibreX is not maintained anymore and they forked it (hnhx/librex#276)
- [The Fork](https://github.com/Ahwxorg/LibreY) however does not have any releases and therfore doesn't meet our requirements