Update of gitlab-ci.yml

Now, the Gitlab CI/CD jobs fail with the following error:

$ yum install -y libgfortran make atlas
Loaded plugins: changelog, fastestmirror, kernel-module, ovl, protectbase,
              : tsflags, versionlock 
Determining fastest mirrors
http://linuxsoft.cern.ch/epel/7/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror. 
To address this issue please refer to the below wiki article
https://wiki.centos.org/yum-errors

This error is related to the end of life CC7 in the end of July. The EPEL archive does not exist anymore.

This PR updates gitlab-ci.yml. It switched to Fedore EPEL mirrors.