Swap Eevee material output with (Cycles) Material Output

Since we started supporting the (Cycles) Material Output old files
stopped working. There is no reason to keep the original Eevee material
otuput anymore.

It includes doversion for old files.

source/blender/gpu/shaders/gpu_shader_material.glsl

@@ -4080,11 +4080,6 @@ void node_eevee_specular(
 	result = Closure(L + emissive.rgb, 1.0 - transp, vec4(ssr_spec, roughness), normal_encode(vN, viewCameraVec), int(ssr_id));
 }
 
-void node_output_eevee_material(Closure surface, out Closure result)
-{
-	result = surface;
-}
-
 #endif /* EEVEE_ENGINE */
 #endif /* VOLUMETRICS */