Improve label in dashboard actions link form

We were using a placeholder to indicate content which should be part of
a label.

It might be better to actually use "Link address" as a label instead of
"URL". I'm using "URL" because it's used in other places in the admin
section.

app/views/links/_link_fields.html.erb

@@ -1,8 +1,7 @@
 <div id="<%= dom_id(f.object) %>" class="nested-fields">
   <div class="small-12 column attachment-actions">
     <%= f.text_field :label %>
-
+    <%= f.text_field :url %>
-    <%= f.text_field :url, placeholder: t("links.link_fields.url_placeholder") %>
 
     <div class="action-remove text-right">
       <%= render_destroy_element_link(f, f.object) %>

config/locales/en/activerecord.yml

@@ -500,7 +500,7 @@ en:
         user: Executed by
       link:
         label: Title
-        url: Link
+        url: URL
       valuator:
         description: Description
         valuator_group_id: Valuator group

config/locales/en/general.yml

@@ -952,8 +952,6 @@ en:
       title: Links
       note: Add the links that are of interest
       add_new_link: Add new link
-    link_fields:
-      url_placeholder: Link address
   communities:
     show:
       surveys: Surveys

config/locales/es/activerecord.yml

@@ -500,7 +500,7 @@ es:
         user: Ejecutado por
       link:
         label: Título
-        url: Enlace
+        url: URL
       valuator:
         description: Descripción
         valuator_group_id: Grupo de evaluación

config/locales/es/general.yml

@@ -952,8 +952,6 @@ es:
       title: Enlaces
       note: Añade los enlaces que sean de interés.
       add_new_link: Añadir nuevo enlace
-    link_fields:
-      url_placeholder: Dirección del enlace
   communities:
     show:
       surveys: Encuestas