[CodeGen] Remove unused declaration createVLIWSched

The declaration was added without a corresponding function by:

  commit cc3bb85
  Author: James Nagurne <[email protected]>
  Date:   Fri Oct 22 17:08:16 2021 -0500

Author: kazutakahirata

llvm/include/llvm/CodeGen/VLIWMachineScheduler.h

@@ -264,8 +264,6 @@ class ConvergingVLIWScheduler : public MachineSchedStrategy {
 #endif
 };
 
-ScheduleDAGMILive *createVLIWSched(MachineSchedContext *C);
-
 } // end namespace llvm
 
 #endif // LLVM_CODEGEN_VLIWMACHINESCHEDULER_H