meson: set the minimum version correctly

Currently we ask for 0.42, but we actually require 0.43 because we pass
file objects as arguments to tests. If someone needs version 0.42 it
wouldn't be hard, just a lot of replacing files() with strings.

Signed-off-by: Dylan Baker <dylan.c.baker@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>