Move initialization of FullstopCenteredFlag out
of ImplFontMetricData::ImplInitTextLineSize since it has
nothing to do with text lines.

Change-Id: I1c2e383d980514c8727d736a3158325c1e0ccfda
Reviewed-on: https://gerrit.libreoffice.org/44712Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mark Hung <marklh9@gmail.com>