Revert "tdf#123313 sw: workaround Undo problem with ToX Update"

This reverts commit 60ea01af - it was
quite simply a bad idea, and only pushed due to lack of time...

Much better to refactor things so that any new CrossRefHeadingBookmark
are inserted (with SwUndoInsBoomark) *before* nodes are inserted into
the ToX.

However! This patch does not fix the problem yet; that needs some more
significant changes.

Change-Id: If22e43b6a2112e5f53d0186bb7bed3ee007fe727
Reviewed-on: https://gerrit.libreoffice.org/71322Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
Tested-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit eca4f30e)
Reviewed-on: https://gerrit.libreoffice.org/71375
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>