[TASK] Deprecate uc->classicPageEditMode and editRegularContentFromId

There is some leftover, never-called code in a regular TYPO3 instance
regarding the old uc->classicPageEditMode option and its companion
functionality in EditDocumentController->editRegularContentFromId
which has been marked for deprecation.

Resolves: #66905
Releases: master
Change-Id: I0a428e411b9d7a0a646c7356d773a369c9397dde
Reviewed-on: http://review.typo3.org/39474


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>