vulkan: Make projection matrix match GL

vulkan: Make projection matrix match GL

Vulkan has a different initial coordinate system to GL.

GL:
(-1, 1, -1) +------+.
            |`.    | `.
            |  `·--|---·
            |   :  |   :
            +------+.  :
             `. :    `.:
               `·------· (1, -1, 1)

Vulkan:
(-1, -1, 0) +------+.
            |`.    | `.
            |  `·--|---·
            |   :  |   :
            +------+.  :
             `. :    `.:
               `·------· (1, 1, 1)

so adjust the near and far plane we pass to
graphene_matrix_init_ortho() to make it end up with the same
projection as the GL renderer.