[InstCombine] Remove unused variable in InstCombineCompares.cpp (NFC)

/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:3190:14:
 error: unused variable 'CmpBW' [-Werror,-Wunused-variable]
    unsigned CmpBW = Ty->getScalarSizeInBits();
             ^
1 error generated.

Author: DamonFool

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -3187,7 +3187,6 @@ Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
   Value *V;
   if (match(X, m_ZExt(m_Value(V)))) {
     Type *NewCmpTy = V->getType();
-    unsigned CmpBW = Ty->getScalarSizeInBits();
     unsigned NewCmpBW = NewCmpTy->getScalarSizeInBits();
     if (shouldChangeType(Ty, NewCmpTy)) {
       if (CR.getActiveBits() <= NewCmpBW) {