[clang][CGBlocks] Remove unused variable "refType" [NFC]

Without the change gcc warned like
 ../../clang/lib/CodeGen/CGBlocks.cpp:965:21: warning: unused variable 'refType' [-Wunused-variable]
   965 |     } else if (auto refType = type->getAs<ReferenceType>()) {
       |                     ^~~~~~~

clang/lib/CodeGen/CGBlocks.cpp

@@ -962,7 +962,7 @@ llvm::Value *CodeGenFunction::EmitBlockLiteral(const CGBlockInfo &blockInfo) {
       }
 
     // If it's a reference variable, copy the reference into the block field.
-    } else if (auto refType = type->getAs<ReferenceType>()) {
+    } else if (type->getAs<ReferenceType>()) {
       Builder.CreateStore(src.emitRawPointer(*this), blockField);
 
       // If type is const-qualified, copy the value into the block field.