Remove duplicate line in vignette

Description

No issue. Self explained.

[ ] My PR is based on a package issue and I have explicitly linked it.
[ ] I have included the target issue or issues in the PR title in the for Issue(s) issue-numbers: PR title
[ ] I have read the contribution guidelines.
[ ] I have tested my changes locally.
[ ] I have added or updated unit tests where necessary.
[ ] I have updated the documentation if required.
[ ] My code follows the established coding standards.
[ ] I have added a news item linked to this PR.
[ ] I have reviewed CI checks for this PR and addressed them as far as I am able.