ce-vpn-page: Fix layout of Identity page
b291e98c (see !2062 (merged)) introduced a scrolled window, but forgot to update the C code to use the new box instead. Now we use it correctly again.
Fixes #2795 (closed)
Compare the screenshot from before at #2795 (closed) with the one after at NetworkManager-openconnect#114.
Edited by Matthijs Velsink