network service: Remove obsolete TODO in CreateUploadDataStream.

There is no longer content/browser/loader/upload_data_stream_builder.cc
since r682406.

Change-Id: I85825d2d040a3d6d9a452847069fa25253054d4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880501Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709845}

services/network/url_loader.cc

@@ -191,7 +191,6 @@ class RawFileElementReader : public net::UploadFileElementReader {
   DISALLOW_COPY_AND_ASSIGN(RawFileElementReader);
 };
 
-// TODO: copied from content/browser/loader/upload_data_stream_builder.cc.
 std::unique_ptr<net::UploadDataStream> CreateUploadDataStream(
     ResourceRequestBody* body,
     std::vector<base::File>& opened_files,