[release-monitoring] Fix the docs build

The package from PyPI doesn't have sphinx-build-3 command, but instead has only
sphinx-build command. Let's use it instead.

Signed-off-by: Michal Konečný <mkonecny@redhat.com>

roles/openshift-apps/release-monitoring/templates/buildconfig.yml

@@ -59,7 +59,7 @@ items:
                 pushd docs && \
                 mkdir -p images && \
                 python3 generate_db_schema && \
-                sphinx-build-3 -b html . _build/html && \
+                sphinx-build -b html . _build/html && \
                 mkdir -p ../anitya/static/docs/ && \
                 cp -r _build/html/* ../anitya/static/docs/ && \
                 popd && \