Update bootstrap css cleanup

[JoachimTillessen]

• rather 1-story 1-commit than sub-atomic commits

• commit title is meaningful => git history search

• commit description is helpful => helps the reviewer to understand the changes

• code is up-to-date with the latest developments of the target branch (rebased to it or whatever) => ⏩-merge for linear history is favoured

• added code is linted

• tests are passing (at least locally): we still have some random test failure on CI. thinking of asking spec/examples.txt to be commited

• in case the changes are visible to the end-user,  video or screenshots should be added to the PR => helps with user testing

• testing coverage improvement is improved.

• CHANGELOG :  add a bullet point on top (optional: reference to github issue/PR )

• parallele PR for documentation  on docusaurus  if the feature/fix is tagged for a release

[github-actions]

LCOV of commit 7ff24f5 during Continuous Integration #3943

Summary coverage rate:
  lines......: 65.5% (14012 of 21402 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions]

LCOV of commit ad6bbac during Continuous Integration #3945

Summary coverage rate:
  lines......: 65.5% (14012 of 21402 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[maiwald]

Selects are looking good! 👍