Remove unused code to display polls with no dates

When this code was added, in commit 1a20a3ce4, we had no validation
rules checking the presence of the start and end dates of a poll. Now we
do, so we don't have to check this condition in the view.

app/components/polls/poll_component.rb

@@ -9,10 +9,6 @@ class Polls::PollComponent < ApplicationComponent
   private
 
     def dates
-      if poll.starts_at.blank? || poll.ends_at.blank?
+      I18n.t("polls.dates", open_at: l(poll.starts_at.to_date), closed_at: l(poll.ends_at.to_date))
-        I18n.t("polls.no_dates")
-      else
-        I18n.t("polls.dates", open_at: l(poll.starts_at.to_date), closed_at: l(poll.ends_at.to_date))
-      end
     end
 end

config/locales/en/general.yml

@@ -569,7 +569,6 @@ en:
         share: "And if you also do me the great favor of sharing my proposal with your friends, family and contacts, it would be perfect!"
   polls:
     all: "All"
-    no_dates: "no date assigned"
     dates: "From %{open_at} to %{closed_at}"
     final_date: "Final recounts/Results"
     index:

config/locales/es/general.yml

@@ -569,7 +569,6 @@ es:
         share: "Y si además, me haces el gran favor de compartir mi propuesta con tus amigos, familiares y contactos ¡sería perfecto!"
   polls:
     all: "Todas"
-    no_dates: "sin fecha asignada"
     dates: "Desde el %{open_at} hasta el %{closed_at}"
     final_date: "Recuento final/Resultados"
     index: