Multiple runs of a field weren't exported as
tracked deletion, resulting bad DOCX export
with reappearing deleted fields in LO and
invalid document in MSO.

Change-Id: I2a1957371b78e0af60d8bf3944a1c28abe8ba0cc
Reviewed-on: https://gerrit.libreoffice.org/73438
Tested-by: Jenkins
Reviewed-by: László Németh <nemeth@numbertext.org>