i965: Don't request GLSL IR lowering of gl_VertexID

i965: Don't request GLSL IR lowering of gl_VertexID

Let the lowering in NIR handle it instead.

This hurts one shader that occurs twice in shader-db (SynMark GSCloth)
on IVB and HSW.  No other shaders or platforms were affected.

total cycles in shared programs: 253438422 -> 253438426 (0.00%)
cycles in affected programs: 412 -> 416 (0.97%)
helped: 0
HURT: 2

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Antia Puentes <apuentes@igalia.com>