Disable JavaScript in notification digest spec

This test has been failing many times because it checks the database
after starting the process running the browser.

We're disabling JavaScript like we do in every other test using the
`create_proposal_notification` method. This way, Capybara will use the
rack driver and there'll be no risk of errors that currently might take
place if both the process running the browser and the process running the
test access the database.

spec/system/emails_spec.rb

@@ -258,7 +258,7 @@ describe "Emails" do
   end
 
   context "Proposal notification digest" do
-    scenario "notifications for proposals that I'm following" do
+    scenario "notifications for proposals that I'm following", :no_js do
       Setting["org_name"] = "CONSUL"
       user = create(:user, email_digest: true)