docs/3638/remove-zenhub-refs

[Nereboss]

Remove references of ZenHub from the Docs

Closes: #3638

Description

Removes references of zenhub from the Readme and feedback GH-page as we are no longer using zenhub.

Definition of Done

A PR is only ready for merge once all the following acceptance criteria are fulfilled:

• Changes have been manually tested
• All TODOs related to this PR have been closed
• There are automated tests for newly written code and bug fixes
• All bugs discovered while working on this PR have been submitted as issues (if not already an open issue)
• Documentation (GH-pages, analysis/visualization READMEs, parser READMEs, --help, etc.) has been updated (almost always necessary except for bug fixes)
• CHANGELOG.md has been updated

Screenshots or gifs

[Nereboss]

Before merging this, we should decide whether to make the new board public (and if so, adjust the Changelog)

[sonarcloud]

Quality Gate passed for 'CodeCharta Visualization'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[sonarcloud]

Quality Gate passed for 'CodeCharta Analysis'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud