[NFC] Fix incorrect use of UNREFERENCED_PARAMETER macro (#6806)

In CalcResTypeSize function, UNREFERENCED_PARAMETER macro is used with a
parameter which is referenced in return statement. That macro was added
in
    6ee4074a4b but it was not removed when
"DxilModule &M" was referenced in
86073a3b0b
    
This fixes the following compiler error with clang 18.1.8 with mingw-w64
toolchain.
    
DxilContainerReflection.cpp:1512:3: error: object of type 'DxilModule'
cannot be assigned because its copy assignment operator is implicitly
deleted
     1512 |   UNREFERENCED_PARAMETER(M);
          |   ^
    winnt.h:1387:40: note: expanded from macro 'UNREFERENCED_PARAMETER'
     1387 | #define UNREFERENCED_PARAMETER(P) {(P) = (P);}
          |                                        ^

lib/HLSL/DxilContainerReflection.cpp

@@ -1509,7 +1509,6 @@ void CShaderReflectionConstantBuffer::Initialize(
 }
 
 static unsigned CalcResTypeSize(DxilModule &M, DxilResource &R) {
-  UNREFERENCED_PARAMETER(M);
   Type *Ty = R.GetHLSLType()->getPointerElementType();
   if (R.IsStructuredBuffer()) {
     Ty = dxilutil::StripArrayTypes(Ty);