Can we only add values to enums?

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.5/static/sql-altertype.html
Description:

I need to add a value to an enum, so I found this page, which answered my
question. However, I found it quite confusing that it only documents adding
a value. I would expect it to also document how to remove a value from an
enum? Is this not possible? If not, I consider it a bug. But either way, if
it is not possible, you should explicitly document it on this page.