Merge commit '7b04dc15c5745e780ff19aaff3d43aa1c6c99ad6' into master

Upgrade flatbuffers to the latest.  It has been a while.

Change-Id: I6c56d742469591f31bd54243ec6d12c4cf397b26
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
diff --git a/third_party/flatbuffers/BUILD.bazel b/third_party/flatbuffers/BUILD.bazel
index 11cc7f1..6f92eec 100644
--- a/third_party/flatbuffers/BUILD.bazel
+++ b/third_party/flatbuffers/BUILD.bazel
@@ -50,6 +50,7 @@
         "include/flatbuffers/detached_buffer.h",
         "include/flatbuffers/flatbuffer_builder.h",
         "include/flatbuffers/flatbuffers.h",
+        "include/flatbuffers/flex_flat_util.h",
         "include/flatbuffers/flexbuffers.h",
         "include/flatbuffers/grpc.h",
         "include/flatbuffers/hash.h",