[third] Bootstrap bug fixup - dropdowns not closing on fix

Some time between the 2.0.4 and the 2.1.0 upgrade, Bootstrap broke in
a way such that clicking on a dropdown did not cause it to close.

Here's the bug thread about it:
https://github.com/twitter/bootstrap/issues/4497

I've implemented this workaround discussed there, though the bug is
fixed in 2.1.1, so when we upgrade this will go away (which is why I
only reluctantly tag it 'third', since the diff will not need to be
carried forward.)

(imported from commit f8d9cf65b33306a426d864c9b503bb3446614111)

zephyr/static/third/bootstrap/js/bootstrap.js

@@ -717,7 +717,7 @@
     $('html')
       .on('click.dropdown.data-api touchstart.dropdown.data-api', clearMenus)
     $('body')
-      .on('click.dropdown touchstart.dropdown.data-api', '.dropdown', function (e) { e.stopPropagation() })
+      .on('click.dropdown touchstart.dropdown.data-api', '.dropdown form', function (e) { e.stopPropagation() })
       .on('click.dropdown.data-api touchstart.dropdown.data-api'  , toggle, Dropdown.prototype.toggle)
       .on('keydown.dropdown.data-api touchstart.dropdown.data-api', toggle + ', [role=menu]' , Dropdown.prototype.keydown)
   })