[TASK] Use label "default" instead of "none" for Space before/after

Change the misleading label "none" to "default" for the following fields
in tt_content: `space_before_class` & `space_after_class`.

The label "none" is misleading because by default the element will have
some spacing before/after by default, derived from the integration.

Resolves: #87716
Releases: master
Change-Id: I4a0cabe70174900b2d403e9756efb2748508dd3a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63528


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Eßl <indy.essl@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Eßl <indy.essl@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>