Removes rake task to send proposal notifications

This action will be performed manually by admin users from the `admin/system_emails` view.

lib/tasks/emails.rake

@@ -1,17 +0,0 @@
-namespace :emails do
-
-  desc "Sends email digest of proposal notifications to each user"
-  task digest: :environment do
-    User.email_digest.find_each do |user|
-      email_digest = EmailDigest.new(user)
-      begin
-        email_digest.deliver
-        email_digest.mark_as_emailed
-      rescue
-        user.increment_counter(:failed_email_digests_count)
-        user.save
-      end
-    end
-  end
-
-end