Fixes #32245 - No host by default in database.yml.example

In dc0983d58937a064d74d96f311ca10a88569480b the example database
configuration file always sets a host. Using a host means PostgreSQL
can't use ident auth which means you must set a password. By commenting
it out, you can simplify the instructions to (on EL but similar on
Debian):

sudo yum -y install postgresql-server
    sudo postgresql-setup --initdb
    sudo systemctl enable --now postgresql
    sudo -u postgres createuser $USERNAME
    sudo -u postgres createdb --owner=$USERNAME foreman

Otherwise you need to provide a username/password as well and possibly set that up.