Do not duplicate vertical axis labels and gridlines
if same value labels follow each other, because of
the number format and rounding.
Supplement of commit: 7f373a4c

Change-Id: I7a5d8196d4f16024c279fa4417a0c8809fb8aec7
Reviewed-on: https://gerrit.libreoffice.org/73432
Tested-by: Jenkins
Reviewed-by: László Németh <nemeth@numbertext.org>