[TASK] Update Bootstrap to 5.0.0-beta2

This beta fixes various issues related to positioning of tooltips
and popovers.

See https://blog.getbootstrap.com/2021/02/10/bootstrap-5-beta-2/

Commands used:
> yarn upgrade bootstrap@^5.0.0-beta2
> grunt build

Resolves: #93487
Releases: master
Change-Id: Ia320d925eec51a6cdd0fa73398a1a0e4ed70e524
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67688


Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>