Remove old references to the GtkTreeView "rules_hint" property.

[David Hampton]

Log Message:
-----------
Remove old references to the GtkTreeView "rules_hint" property.  This
property is now controlled via the .gtkrc file (where it should be).

Tags:
----
gnucash-gnome2-dev

Modified Files:
--------------
    gnucash/src/gnome/schemas:
        apps_gnucash_dialog_commodities.schemas
        apps_gnucash_dialog_prices.schemas
    gnucash/src/gnome-utils:
        gnc-tree-view-account.c
        gnc-tree-view-commodity.c
        gnc-tree-view-price.c