Remove .mobi and .azw3 e-book formats

This seems like a good call, if it simplifies the process, and makes releasing new editions easier. The article E-Book Formats - Choose the right one for your book from July 2022 has this table, where it can be seen that the three E-book readers support either PDF or ePub:

I updated the e-book build scripts to remove the steps for creating the .mobi and .azw3 files.

Automatically closed - issue fixed for 2 weeks with no activity.