remove and reinsert formula cell from/to tree during CompileXML

... to keep the count updated, which actually silences the dbgutil
warning of ScDocument::RemoveFromFormulaTree() when loading .ods

Change-Id: I8453d688ca673a47fee15c84478262e1da53e408
(cherry picked from commit bfd1909c87d0d645f1bbb74a142172ecc15100e8)