[BUGFIX] Ensure CKEditor5 removePlugins is always a list

And therefore maps into a JSON array instead of an object,
preventing errors when CKEditor5 operated on the resulting
confguration.

Resolves: #102230
Resolves: #102245
Related: #102099
Releases: main, 12.4
Change-Id: Ia20e5927b10bbb56763e3fc01cc30c8c4d0252c8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81538


Tested-by: core-ci <typo3@b13.com>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>