Remove contact form

[mei-li]

Point the submodule to our own fork that has the contact form removed.

To properly update the submodule to the new fork, possible one or more of the following steps will be needed:

rm -rf .git/modules/pelican-fh5co-marble

git rm -f pelican-fh5co-marble
git sumodule update --init pelican-fh5co-marble

# git submodule deinit -f pelican-fh5co-marble

[mei-li]

fixes #28