Feat/testimonial adjust

[vktrrdk]

@dweinholz with https://github.com/deNBI/cloud-api/pull/4720

Includes:

• https://github.com/deNBI/cloud-api/issues/4718
• testimonial: bigger default size textarea #5790
• testimoial: image rigths info #5791
• testimonial: more information what we want #5792

Try to fulfill the following points before the Pull Request is merged:

• Give a meaningfull description for the PR
• The PR is reviewed by one of the team members.
• If a linting PR exists, it must be merged before this PR is allowed to be merged.
• It must be checked if anything in the Readme must be adjusted (development-, production-, setup).
• It must be checked if any section in the wiki (https://cloud.denbi.de/wiki/) should be adjusted.
• If the PR is merged in the master then a release should be be made.
• The PR is responsive on smaller screens.
• If the requirements.txt have changed, check if the patches still work
• If the new code is readable, if not it should be well commented
• In case the code is not well commented: An respectice commenting issue with tag "important" is opened.
• If a squash of commits is required, it has been performed or will be performed at final merge
• Finally a second team member checks if all requirements met

For releases only:

• If the review of this PR is approved and the PR is followed by a release then the .env file
  in the cloud-portal repo should also be updated.