[TASK] styleguide: Remove all type=flex sql field definitions

We're adding core code to add default sql definitions
derived from TCA. Fields of type=flex do not need to
be set anymore.

See: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81158

Releases: main
Related: https://forge.typo3.org/issues/101997