Remove obsolete rake tasks

These tasks dealt with data migrations or stats generations which were
done only once, so we don't need them anymore.

New CONSUL installations don't need these tasks, and existing CONSUL
installations will execute them when upgrading one release at a time.

spec/lib/tasks/settings_spec.rb

@@ -35,72 +35,6 @@ describe Setting do
     end
   end
 
-  describe "#per_page_code_migration" do
-
-    let :run_rake_task do
-      Rake::Task["settings:per_page_code_migration"].reenable
-      Rake.application.invoke_task "settings:per_page_code_migration"
-    end
-
-    context "Neither per_page_code_head or per_page_code Settings exist" do
-      before do
-        Setting.where(key: "per_page_code").first&.destroy
-        Setting.where(key: "per_page_code_head").first&.destroy
-        run_rake_task
-      end
-
-      it "has per_page_code_head setting present and no per_page_code" do
-        expect(Setting.where(key: "per_page_code_head").count).to eq(1)
-        expect(Setting["per_page_code_head"]).to eq(nil)
-        expect(Setting.where(key: "per_page_code").count).to eq(0)
-      end
-    end
-
-    context "Both per_page_code_head or per_page_code Settings exist" do
-      before do
-        Setting["per_page_code"] = "per_page_code"
-        Setting["per_page_code_head"] = "per_page_code_head"
-        run_rake_task
-      end
-
-      it "has per_page_code_head setting present and no per_page_code" do
-        expect(Setting.where(key: "per_page_code_head").count).to eq(1)
-        expect(Setting["per_page_code_head"]).to eq("per_page_code_head")
-        expect(Setting.where(key: "per_page_code").count).to eq(0)
-      end
-    end
-
-    context "per_page_code_head exists, but per_page_code does not" do
-      before do
-        Setting.where(key: "per_page_code").first&.destroy
-        Setting["per_page_code_head"] = "per_page_code_head"
-        run_rake_task
-      end
-
-      it "has per_page_code_head setting present and no per_page_code" do
-        expect(Setting.where(key: "per_page_code_head").count).to eq(1)
-        expect(Setting["per_page_code_head"]).to eq("per_page_code_head")
-        expect(Setting.where(key: "per_page_code").count).to eq(0)
-      end
-    end
-
-    context "per_page_code_head does not exist, but per_page_code does" do
-      before do
-        Setting["per_page_code"] = "per_page_code"
-        Setting.where(key: "per_page_code_head").first&.destroy
-        run_rake_task
-      end
-
-      it "has per_page_code_head setting present and no per_page_code" do
-        expect(Setting.where(key: "per_page_code_head").count).to eq(1)
-        expect(Setting["per_page_code_head"]).to eq("per_page_code")
-        expect(Setting.where(key: "per_page_code").count).to eq(0)
-      end
-    end
-
-  end
-
-
   describe "#rename_setting_keys" do
 
     let :run_rake_task do