Remove old and unused `.readthedocs.yaml` file

[yousefmoazzam]

Unless we find that this file has some use for hosting docs on github pages (the current docs hosting in use for httomo), this can be removed.

[yousefmoazzam]

Is this actually completed? The branch that is the most up to date is probably either gpuloop or docs_update, and both still have this file:

• gpuloop: https://github.com/DiamondLightSource/httomo/blob/gpuloop/.readthedocs.yaml
• docs_update: https://github.com/DiamondLightSource/httomo/blob/docs_update/.readthedocs.yaml

[dkazanc]

sorry, now it is done with 0b053a6c