Use -slim base Docker image for cleaner security dashboard
In https://gitlab.com/gitlab-org/gitter/webapp/-/merge_requests/1788 we moved to an Alpine Linux base image to have lighter containers and clean the security dashboard of issues.
In https://gitlab.com/gitlab-org/gitter/webapp/-/merge_requests/1859 we reverted because E2E tests depended on apt-get
(https://gitlab.com/gitlab-org/gitter/webapp/-/issues/2495) which isn't in Alpine Linux.
This MR moves the Docker image to a Debian Slim base image which has the benefits of Alpine Linux AND the apt-get
command.
Edited by Eric Eastwood