i965/test: Remove the fragment/vertex_program field from test visitors

i965/test: Remove the fragment/vertex_program field from test visitors

None of them are actually using it.  It's a relic of an older compiler
interface that required a gl_program.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>