Fix compilation error under GCC.
Fix compilation error under GCC.

Error message:
error: attribute ignored [-Werror=attributes]
  427 | #define ABSL_MUST_USE_RESULT [[nodiscard]]
      |                              ^
bazel-out/k8-fastbuild/bin/external/com_googlesource_quiche/quiche/quic/core/web_transport_interface.h:49:11: note: in expansion of macro 'ABSL_MUST_USE_RESULT'
   49 |   virtual ABSL_MUST_USE_RESULT ReadResult Read(char* buffer,
PiperOrigin-RevId: 367301659
Change-Id: I9d07e5c8dee0a5f1cc9c4f159d3631f32d674456

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