[TASK] Drop superfluous codeMirror label from FormEngine elements

The classes `T3editorElement` and `JsonElement` boot a CodeMirror
instance and provides a hard-coded label to be rendered in a panel
below the editor.

That label became useless over time as it provides redundant
information and is therefore now removed from those elements.

Resolves: #100433
Releases: main
Change-Id: If387a5141ab5c03c5e367f32d990e34ff59f456b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78441


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>