Revert "Make unicode ranges in font take precedence over codepage"

This reverts commit 3a84d92f
because it caused a regression with certain fonts on Windows that
have divided information about writing system support in unicode
ranges and codepage ranges.

The original commit fixed a problem on Android where one
of the fonts had an entry for Arabic in its codepage range but
no glyphs for this script. This issue has been fixed in a different
way now, by 0b87f4f6

 which makes
fallback fonts work properly, so the commit is no longer needed
to fix said bug.

[ChangeLog][Fonts] Fixed regression in font families returned by
QFontDatabase::families() for certain writing systems.

Task-number: QTBUG-39846
Change-Id: I3077b1e618b21680549abc1734cb6df6e264387e
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>