Update Website for post 3.9.1 release

[ann0see]

Short description of changes This PR finalizes the 3.9.1 release.

Context: Fixes an issue? Related issues

Status of this Pull Request Needs local testing.

What is missing until this pull request can be merged?

Approval and local test

Does this need translation?

NO.

Checklist

• [x] I've verified that this Pull Request follows the general code principles
• [x] I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• [x] I'm sure that this Pull Request goes to the correct branch