Drop incorrect comment.

[whchung]

Closing this patch as this really should be in D79021

mlir/lib/Conversion/GPUCommon/GPUOpsLowering.h

auto llvmFuncOp = rewriter.create<LLVM::LLVMFuncOp>(
           gpuFuncOp.getNumWorkgroupAttributions();
       auto int64Ty = LLVM::LLVMType::getInt64Ty(typeConverter.getDialect());
       for (auto en : llvm::enumerate(gpuFuncOp.getPrivateAttributions())) {
         Value attribution = en.value();
         auto type = attribution.getType().cast<MemRefType>();
         assert(type && type.hasStaticShape() &&
                "unexpected type in attribution");
 
-        // Explicitly drop memory space when lowering private memory
-        // attributions since NVVM models it as `alloca`s in the default
-        // memory space and does not support `alloca`s with addrspace(5).
         auto ptrType = typeConverter.convertType(type.getElementType())
                            .cast<LLVM::LLVMType>()
                            .getPointerTo(AllocaAddrSpace);
         Value numElements = rewriter.create<LLVM::ConstantOp>(
             gpuFuncOp.getLoc(), int64Ty,
             rewriter.getI64IntegerAttr(type.getNumElements()));
         Value allocated = rewriter.create<LLVM::AllocaOp>(
             gpuFuncOp.getLoc(), ptrType, numElements, /*alignment=*/0);