[/genetree] Updated the documentation of the prune_* options

Created by: muffato

Requirements

Description

Updated the documentation of the prune_* options in two gene-tree endpoints (the first one already had the complete description)

Use case

Someone wants to get a smaller tree by removing the species they don't care about. They think "is there an option to prune the tree ?". They go to the documentation and 🎊 there it is

Benefits

People know what the options are doing.

Possible Drawbacks

More text to read. Some people may have preferred the function implemented the other way.

Testing

Have you added/modified unit tests to test the changes?

No

If so, do the tests pass/fail?

Have you run the entire test suite and no regression was detected?

No

Changelog

Are you changing the functionality of an endpoint? If so, please give a one line summary for the public facing changelog.

No