[clang][CGExprConstant] Remove no-op ptr-to-ptr bitcast (NFC)

Remove a call to `getPointerCast` which is effectively does a no-op ptr-to-ptr
bitcast.

Opaque ptr clean-up effort.

clang/lib/CodeGen/CGExprConstant.cpp

@@ -1861,10 +1861,7 @@ class ConstantLValueEmitter : public ConstStmtVisitor<ConstantLValueEmitter,
     if (!hasNonZeroOffset())
       return C;
 
-    llvm::Type *origPtrTy = C->getType();
-    C = llvm::ConstantExpr::getGetElementPtr(CGM.Int8Ty, C, getOffset());
-    C = llvm::ConstantExpr::getPointerCast(C, origPtrTy);
-    return C;
+    return llvm::ConstantExpr::getGetElementPtr(CGM.Int8Ty, C, getOffset());
   }
 };