Update NNAPI Extensions documentation

This is a follow-up to change Ia9b99015eec7a48bbf969cbe503862271f09adca

Bug: 118605927
Test: mma
Change-Id: I7ddafca04bce6fd37a9c0877270cee325111d833
Merged-In: I7ddafca04bce6fd37a9c0877270cee325111d833
(cherry picked from commit 1ffe69a8e9ac0dc0f95accdf8e62a80347e12571)
1 file changed