docs: Fix attr link in support lib docs.

This issue was breaking the build in nyc-docs; Michael made the fix
there, so I'm cherrypicking it back to our doc branches.

Change-Id: Ie15bd056ebf939270dfcd45dda56946ed41b56f0
(cherry picked from commit ae316f842431254ce364cda4f1edde6fe607ab43)
1 file changed