[TASK] Proper core require in styleguide composer.json

Before styleguide has been merged to monorepo, it did
not have composer require definitions to core since
that gave ugly cross dependencies between monorepo
and styleguide repo.

With styleguide being merged into monorepo v13, we
can finally safely set a core requirement just like
all other core extensions do.

Resolves: #102716
Releases: main
Change-Id: Ic6feceab020bccb220ddeb61838b325b40755c0f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82274


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