Disable deprecated declarations for tensorflow

The new flatbuffer deprecated Vector::Length. Disable the warning before
upstream fixes this issue.

This should be part of:
https://android-review.googlesource.com/c/platform/external/tensorflow/+/928187

Exempt-From-Owner-Approval: Disable a warning.
Test: build
Change-Id: I0e0fade251e8b8267fc099ccebfb93c82037bd69