Revert "Fix host:port in requests sent to convertit"

This reverts commit 4f60ccfc39a7306b0ee8d994b592dae08b83f4f6.
Update mapentity.

Previous changes were reverted since integrated in MapEntity itself.

For example, on the frontend template, we don't passe the absolute URL, so
better to run the tests the same way:

https://github.com/makinacorpus/django-mapentity/blob/e7e296dc91f80a2d9fafaf4c8cf3cbd638486be8/mapentity/templates/mapentity/mapentity_detail.html#L13-L14