Remove unused placeholder menu items from student desktop navbar

[theovier]

Description

• Implements issue Remove menu item stubs from student's (desktop) navbar #539
• Closes Remove menu item stubs from student's (desktop) navbar #539

Reason for this PR

• non-working menu stubs should not be included in an MVP

Changes in this PR

• remove non-working menu stubs from the student's desktop navbar. The student's courses menu now only has 1 column as there is only 1 item in it.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Manually tested all use cases this could alter

Test Configuration:

• OS: Windows Mac Linux

• Browser: Firefox Chrome Safari Chromium

• Frontend:

  • Development build

• Backend:

  • No backend needed to test this

Checklist:

• I have performed a self-review of my own code
• My changes generate no new linting warnings or console warnings
• I have updated the CHANGELOG.md to include any changes made in this PR (add WIP to the top, if there is none already)

[tobias-wiese]

We could additionally delete the course menu footer, as it is not needed in our application atm

[theovier]

We could additionally delete the course menu footer, as it is not needed in our application atm

done.