Fix "What's this?" on admin dashboard

When a user has no enterprises, the admin dashboard displays a "What's
this?" hint in the right corner of the enterprises tab. The link text
and the tooltip were both broken (missing translation).

app/views/spree/admin/overview/_enterprises_header.html.haml

@@ -7,4 +7,4 @@
         = t "spree_admin_enterprises_create_new"
   - else
     %a{ "ofn-with-tip" => t('.ofn_with_tip') }
-      = t "admin_enterprise_groups_what_s_this"
+      = t "admin.whats_this"

config/locales/en.yml

@@ -1013,9 +1013,6 @@ en:
     shared:
       user_guide_link:
         user_guide: User Guide
-    overview:
-      enterprises_header:
-        ofn_with_tip: Enterprises are Producers and/or Hubs and are the basic unit of organisation within the Open Food Network.
       enterprises_hubs_tabs:
         has_no_payment_methods: "%{enterprise} has no payment methods"
         has_no_shipping_methods: "%{enterprise} has no shipping methods"
@@ -3001,6 +2998,8 @@ See the %{link} to find out more about %{sitename}'s features and to start using
             distributor: "Distributor:"
             order_cycle: "Order cycle:"
       overview:
+        enterprises_header:
+          ofn_with_tip: Enterprises are Producers and/or Hubs and are the basic unit of organisation within the Open Food Network.
         products:
           active_products:
             zero: "You don't have any active products."