scripts/ci: update gitlab-runner playbook to handle CentOS

scripts/ci: update gitlab-runner playbook to handle CentOS

This was broken when we moved to using the pre-built packages as we
didn't take care to ensure we used RPMs where required.

NB: I could never get this to complete on my test setup but I suspect
this was down to network connectivity and timeouts while downloading.

Fixes: 69c4befba1 (scripts/ci: update gitlab-runner playbook to use latest runner)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230315174331.2959-5-alex.bennee@linaro.org>