Fix sanity: check_sources_and_headers
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index bca5652a..01b563d 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -822,6 +822,7 @@
include/grpc++/impl/codegen/server_context.h \
include/grpc++/impl/codegen/server_interface.h \
include/grpc++/impl/codegen/service_type.h \
+include/grpc++/impl/codegen/slice.h \
include/grpc++/impl/codegen/status.h \
include/grpc++/impl/codegen/status_code_enum.h \
include/grpc++/impl/codegen/status_helper.h \