Log Message:
*: Remove manual page entries from ALTERNATIVES files.

Thes are not supported by pkg_alternatives, and lead to breakage as found
in <http://mail-index.netbsd.org/tech-pkg/2020/05/06/msg023089.html>.

In many cases these were unnecessary anyway, as they match the corresponding
command that pkg_alternatives will have automatically detected manual page
entries for, plus many of them did not support PKGMANDIR.

In the one case (databases/py-peewee) where the manual page does not match
the command name, pkg_alternatives will need to be enhanced to support this
before it can be re-enabled.