[BUGFIX] No CORS Error in WS preview

We should not manipulate document.domain in workspace preview as we need
to communicate with our parent master window.

Releases: master, 8.7
Resolves: #78401
Change-Id: Id3f581545a5547ca4ab8c46ee204b1c947ff6e56
Reviewed-on: https://review.typo3.org/56843


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>