`invoke docs -r` doesn't clean generated api files

[chenkasirer]

Not all API auto generated files are cleaned when using the clean flag (-r) with invoke docs -r.

Can cause sphinx to break when changes are made to the documented package API structure.

A clear and concise description of what the bug is.

To Reproduce

Not sure exactly, maybe removed modules remain stale in the generated files.

Expected behavior

All auto generated files should be wiped.