docs: Removed support libraries from API Guide TOC

See (e.g.) TOC on http://go/dods-stage/guide/ to verify it.
Previously (e.g. on https://developer.android.com/guide/ )
you'd see a "Libaries" menu item between "Data Storage" and
"Administration"; that's gone now.

Already made this change in Critique (http://cr/134027548) but since
we're still publishing docs from Gerrit, thought it's best to
back-port this change.

bug: 31607475
Change-Id: I40ff0bebf76305dcad3ef0fc6fbe271b4a625a57

docs/html/guide/_book.yaml

@@ -399,11 +399,6 @@ toc:
   - title: App Install Location
     path: /guide/topics/data/install-location.html
 
-- title: Libraries
-  path: /topic/libraries/index.html
-  section:
-  - include: /topic/libraries/_book.yaml
-
 - title: Administration
   path: /guide/topics/admin/index.html
   section: