Remove linux/s390x build for now

[Pierre-Gilles]

Pull Request check-list

To ensure your Pull Request can be accepted as fast as possible, make sure to review and check all of these items:

• If your changes affects code, did your write the tests?
• Are tests passing? (npm test on both front/server)
• Is the linter passing? (npm run eslint on both front/server)
• Did you run prettier? (npm run prettier on both front/server)
• If you are adding a new features/services, did you run integration comparator? (npm run compare-translations on front)
• If your changes modify the API (REST or Node.js), did you modify the API documentation? (Documentation is based on comments in code)
• If you are adding a new features/services which needs explanation, did you modify the user documentation? See the GitHub repo and the website.
• Did you add fake requests data for the demo mode (front/src/config/demo.json) so that the demo website is working without a backend? (if needed) See https://demo.gladysassistant.com.

NOTE: these things are not required to open a PR and can be done afterwards / while the PR is open.

Description of change

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[codecov]

Codecov Report

Merging #1068 (d6230b8) into master (9bbe54d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1068   +/-   ##
=======================================
  Coverage   94.96%   94.96%           
=======================================
  Files         524      524           
  Lines        6948     6948           
=======================================
  Hits         6598     6598           
  Misses        350      350           

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