🐛 site.yml: Remove start_path to fix build script

This commit removes the `start_path` parameter from the `site.yml`
Antora config file, because it is simply not needed anymore! In the
previous repository structure, the docs were in a `docs/` directory in
the root folder, but now, the Antora tree is in the root directory of
this dedicated `commops/docs` repository.

I realized this change needed to be made while I was trying to build the
docs locally, and the script gave me an error that it could not find the
source content.

Signed-off-by: Justin Wheeler <jwheel@redhat.com>

site.yml

@@ -5,7 +5,6 @@ content:
   sources:
    - url: .
      branches: HEAD
-     start_path: docs
 ui:
   bundle:
     url: https://gitlab.com/fedora/docs/docs-website/ui-bundle/-/jobs/artifacts/HEAD/raw/build/ui-bundle.zip?job=bundle-stable