[NAN] Update API javadoc to clarify NAN status change broadcast scope

(cherry-pick of commit 1fceaf9d63cd572cad57e71f6cb66f0cb59183b5)

Bug: 31675932
Test: make -j 32 update-api (to generate doc)
Change-Id: I7263a15902c423c1c71c2c457c82e8caef5abceb
1 file changed