[TASK] Have static DP in ReactionsRepositoryTest

Avoid a useless helper method by having
object creation within data provider
directly.

Resolves: #100448
Related: #100249
Releases: main
Change-Id: I630a7f24fe0b5e295d924a83553c85d648d15390
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78462


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>