Update flatbuffers to v2.0.5 (#72132)

Summary:
This updates flatbuffer submodule from v1.12.1 to v2.0.5, but according to relnotes on [v2.0.0](https://github.com/google/flatbuffers/releases/tag/v2.0.0):
> Note, "2.0" doesn't signify any kind of major overhaul of FlatBuffers, it is merely trying to be more semver compatible, and this release does have breaking changes for some languages much like all releases before it.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/72132

Reviewed By: seemethere

Differential Revision: D33923945

Pulled By: malfet

fbshipit-source-id: 9398d35f6bbc4ec05562a25f6ee444b66df94086
(cherry picked from commit 2335d5f69b0b0ee36ead7f5d66cfc47a1954f834)
diff --git a/third_party/flatbuffers b/third_party/flatbuffers
index 697147a..d0cede9 160000
--- a/third_party/flatbuffers
+++ b/third_party/flatbuffers
@@ -1 +1 @@
-Subproject commit 697147a2e686486424b9d15fc3e1612586a60f97
+Subproject commit d0cede9c90c5257537c293517a21376408b549fa