[release-monitoring] Install alembic using pip

I'm running out of ideas, but it seems that the python3-alembic package isn't
visible as a module for /bin/python3 and alembic command doesn't see `anitya`
module. So let's try to install alembic from pip and see if this helps.

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

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

@@ -23,7 +23,6 @@ items:
                 fedora-messaging \
                 npm \
                 poetry \
-                python3-alembic \
                 python3-beautifulsoup4 \
                 python3-arrow \
                 python3-dateutil \
@@ -47,6 +46,7 @@ items:
         # This is needed because the version 1.7.0 currently available in Fedora
         # doesn't work with sphinx 5+ and fails when building documentation
         RUN pip-3 install sphinxcontrib-httpdomain
+        RUN pip-3 install alembic
         RUN git clone https://github.com/fedora-infra/anitya.git && \
                 pushd anitya && \
 {% if env == 'staging' %}