mail/getmail6: fix build errors on package-as-user
This build fails as user, because in python3 pycache files are always
created with root as owner. Therefore, the @${CHMOD} command in
post-install: fails when run as user. Upon closer inspection, the
@${CHMOD} operation is superfluous. File permissions in the final package
are fine without it.
PR: 249175
Submitted by: m.bueker@berlin.de (maintainer)