Update llpc to handle new version of llvm (#2801)

Handle upstream llvm changes for llvm/llvm-project@2400c54
[Vectorize] Remove Transforms/Vectorize.h (#71294)

We should use "llvm/Transforms/Vectorize/LoadStoreVectorizer.h" instead
now, but we do not actually need it here.

llpc/lower/llpcSpirvLower.cpp

@@ -81,7 +81,6 @@
 #include "llvm/Transforms/Scalar/SimplifyCFG.h"
 #include "llvm/Transforms/Utils.h"
 #include "llvm/Transforms/Utils/Mem2Reg.h"
-#include "llvm/Transforms/Vectorize.h"
 
 #define DEBUG_TYPE "llpc-spirv-lower"