Use the same texts on event links and graphs

Note we're delegating the `t` method because i18n-tasks doesn't detect
code like `ApplicationController.helpers.t` and so reports we aren't
using the `admin.stats.graph` translations.

spec/controllers/admin/api/stats_controller_spec.rb

@@ -29,7 +29,7 @@ describe Admin::Api::StatsController, :admin do
         get :show, params: { event: "proposal_created" }
 
         expect(response).to be_ok
-        expect(response.parsed_body).to eq "x" => ["2015-01-01", "2015-01-02"], "Proposal Created" => [2, 1]
+        expect(response.parsed_body).to eq "x" => ["2015-01-01", "2015-01-02"], "Citizen proposals" => [2, 1]
       end
     end
   end