fix: Remove empty python bindings documentation

The python bindings documentation doesn't exist yet but the build system
contains remnants of the bt1 doc. Moreover, it contains a Sphinx theme
without any copyright or licensing information which makes our distro
friends a bit nervous.

Remove everything for now, it can be re-introduced when the doc is
actually written.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Change-Id: I11b23822c8bf98c54a88c7e856d606d01102797f
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2941
Reviewed-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>