Fixes an Envoy continuous integration build error:
Fixes an Envoy continuous integration build error:

external/com_github_google_quiche/quiche/http2/adapter/test_utils.cc: In member function ‘virtual bool http2::adapter::test::TestDataFrameSource::Send(absl::string_view, size_t)’:
external/com_github_google_quiche/quiche/http2/adapter/test_utils.cc:64:46: error: type qualifiers ignored on cast result type [-Werror=ignored-qualifiers]
   64 |   } else if (static_cast<const size_t>(result) < concatenated.size()) {
      |

PiperOrigin-RevId: 449212715

google/quiche,google/quiche,google/quiche,google/quiche