oeqa/buildgalculator.py: Add dependency on gtk+3

This helps in skipping this test on images which are not using gtk and
as per the gcalculator website it needs gtk+3 or gtk+2 and libglade as
the build first looks for gtk+3

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>