Drop Ubuntu 20.04 support

[submarcos]

Description

Related Issue

Checklist

• I have followed the guidelines in our Contributing document
• My code respects the Definition of done available in the Development section of the documentation
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes
• I added an entry in the changelog file
• My commits are all using prefix convention (emoji + tag name) and references associated issues
• I added a label to the PR corresponding to the perimeter of my contribution
• The title of my PR mentionned the issue associated

[cypress]

Geotrek-admin    Run #15124

Run Properties:   Passed #15124  •  f84343ca17 ℹ️: Merge 62ee749c3534134011ec84d7b22fd39a5e116bef into 6d42781cc7a9e6d5def24ea97d00...

Project	Geotrek-admin
Branch Review	refs/pull/5119/merge
Run status	Passed #15124
Run duration	02m 09s
Commit	f84343ca17 ℹ️: Merge 62ee749c3534134011ec84d7b22fd39a5e116bef into 6d42781cc7a9e6d5def24ea97d00...
Committer	Jean-Etienne Castagnede
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	22
View all changes introduced in this branch ↗︎

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.46%. Comparing base (6d42781) to head (62ee749).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5119      +/-   ##
==========================================
- Coverage   98.47%   98.46%   -0.01%     
==========================================
  Files         272      272              
  Lines       22285    22285              
==========================================
- Hits        21945    21944       -1     
- Misses        340      341       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

Pull request overview

This PR removes support for Ubuntu 20.04 (Focal Fossa) from the Geotrek-admin project as a breaking change. The changes streamline CI/CD pipelines and build processes by removing focal-specific build configurations, test matrices, and deployment steps that are no longer needed.

Key changes:

• Removed Ubuntu Focal 20.04 from all CI/CD test and build matrices
• Cleaned up Dockerfile to remove focal-specific PPA and repository configurations
• Updated deployment workflows to exclude focal package publishing

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
docs/changelog.rst	Documents the breaking change announcement for Ubuntu 20.04 deprecation
docker/Dockerfile.debian.builder	Removes focal-specific PPA setup and repository configuration for dh-virtualenv
.github/workflows/test.yml	Removes 'focal-3.10' from test/coverage matrices, removes focal-specific Python venv installation, removes focal debian artifact download, and removes focal package deployment commands

Critical Issue Found: While the CI/CD and build configuration changes are complete and correct, the documentation in docs/installation-and-configuration/upgrade.rst still contains multiple references to Ubuntu Focal 20.04 that need to be updated or removed to ensure consistency with this breaking change.

[submarcos]

@copilot open a new pull request to apply changes based on the comments in this thread

[Copilot]

@submarcos I've opened a new pull request, #5124, to work on those changes. Once the pull request is ready, I'll request review from you.