Prevent costly session#refresh when switching from visual to content editor

CMS-13358 introduces a session refresh when switching from visual to content editor and vice versa.

The reason to refresh the session were warnings that the transferable property of the draft document was out of sync. That was caused by faulty use of scxml ( See CMS-13409 ).
CMS-13409 removes on-entry modification of properties of the draft variant.
So the "transferable" property is not out-of-sync anymore.
So the session refresh can be removed.

The removal of the session refresh did not cause the warning again.