Update .gitlab-ci.yml

Description

Temporary comment out linting and doc jobs. Tests must pass as usual.

Consequences:

• lint score badge has outdated score, will expire altogether after some time (about 3 weeks)
• documentation won't be automatically updated and published on our gitlab pages website
  • anyway, the gitlab pages website is down.

As soon as we hear back from the DESY GitLab admins about the fix, these features will be re-eanbled. In case the fix won't be provided in a reasonable time (e.g. by Christmas), we will implement certain workarounds

Related Issue

Closes #38 (closed)

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.