[BUGFIX] Set active class on link of initially active tab

Since bootstrap 5 an active tab is highlighted by setting the
`.active` class on the tab item link (`.nav-link`) instead of
the tab item (`.nav-item`) itself.

Therefore, this must also be done in templates defining the
initially active tab item, which is usually just the first one.

See: https://getbootstrap.com/docs/5.0/components/navs-tabs/#fill-and-justify

Resolves: #93763
Releases: master
Change-Id: I56f7024a3b4d7f62e01e8dc9e25d508203359366
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68471


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>