accounts-dialog: subdialog window should not resizeable
accounts-dialog: subdialog window should not resizeable

This means that when the expanded for advanced option is opened/closed the
dialog maintains the correct size.

https://bugzilla.gnome.org/show_bug.cgi?id=687338

GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets