[Refactor] (Program): stop ProgramObject.h including SpvcSession.h - it names no spirv-cross or SPIRV-Reflect symbol

- The include line was the header's only match for spvc_*/SpvReflect*/SpvcMetadata/
  SpvcSession; it only ever forwarded <spirv_reflect.h> and the session type to the
  eight includers, every one of which builds without it (no consumer needed a direct
  include added).
- One less transpiler header behind ProgramObject.h, on the way to a ProgramArtifacts.h
  closure that stays clear of MG_Util/ShaderTranspiler/ (P0.5 gate A).

MobileGL/MG_State/GLState/ProgramState/ProgramObject.h

@@ -12,7 +12,6 @@
 #include "ProgramArtifacts.h"
 
 #include <MG_Util/Metrics/BufferMetrics.h>
-#include <MG_Util/ShaderTranspiler/SpvcSession.h>
 
 namespace MobileGL::MG_State::GLState {
     // The link job. Only ever held by SharedPtr here, so a forward declaration is enough -