Wiki: simplify default 'host' setting (avoids issues with 0.10.0)
The existing way we do this was intended to use HTTPS by default
back when mwclient did not do that upstream. mwclient started
doing that with 0.8.0 and every supported Fedora and EPEL branch
has at least 0.8.1, so we don't need to worry about that any
more. Simplifying this avoids deprecation warnings on 0.10.0.
Signed-off-by: Adam Williamson <awilliam@redhat.com>