Remove dead code. Should have no effect on behaviour.

Possibly originally the intent was that mbDisableGlyphs would have
been false in most cases on NT-based Windows (all versions that we
support now). However, since dadfc608,
in 2005, mbDisableGlyphs was set to always true in the SimpleWinLayout
ctor.

Change-Id: Id929224d5656706762c2f44ee26c76f8b20ee8b8
Signed-off-by: Michael Meeks <michael.meeks@collabora.com>