Reverting the checkout of plone.app.contentmenu because of jenkins fa…

…ilures

Forgot there are no "Site Administrator" fixes in the
plone.app.contentmenu branch used in 4.3 so the breakages weren't even
about my change, just checking it out seems to have exposed failures.

checkouts.cfg

@@ -1,7 +1,6 @@
 [buildout]
 always-checkout = force
 auto-checkout =
-    plone.app.contentmenu
     plone.app.locales
     plone.app.theming
     plone.app.upgrade