drm/i915/gvt: Remove one extra declaration in scheduler.h

Now the function has been moved into scheduler.c. The extra declaration
is not necessary.
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>

drivers/gpu/drm/i915/gvt/scheduler.h

@@ -147,5 +147,4 @@ intel_vgpu_create_workload(struct intel_vgpu *vgpu, int ring_id,
 
 void intel_vgpu_destroy_workload(struct intel_vgpu_workload *workload);
 
-void release_shadow_wa_ctx(struct intel_shadow_wa_ctx *wa_ctx);
 #endif