Add a text to the links to execute dashboard actions

People using screen readers had no idea what these links were about (not
that the icons are very usable for people seeing them either... but
that's a different topic). Axe was reporting this error:

```
link-name: Links must have discernible text (serious)
https://dequeuniversity.com/rules/axe/4.10/link-name?application=axeAPI
The following 1 node violate this rule:

  Selector: #dashboard_action_2_execute
  HTML: <a id="dashboard_action_2_execute" class="unchecked-link"
           rel="nofollow" data-method="post"
           href="/proposals/16-proposal-6-title/dashboard/actions/2/execute">
          <span class="unchecked"></span>
        </a>
  Fix all of the following:
  - Element is in tab order and does not have accessible text
  Fix any of the following:
  - Element does not have text that is visible to screen readers
  - aria-label attribute does not exist or is empty
  - aria-labelledby attribute does not exist, references elements that
    do not exist or references elements that are empty
  - Element has no title attribute
```

config/locales/en/general.yml

@@ -475,6 +475,8 @@ en:
       see_proposed_actions: Check out recommended actions
       hide_proposed_actions: Hide recommended actions
       pending_title: Pending
+      execute: "Mark %{name} as done"
+      unexecute: "Unmark %{name} as done"
       show_description: Show description
       without_pending_actions: No recommended actions pending
       done_title: Done

config/locales/es/general.yml

@@ -475,6 +475,8 @@ es:
       see_proposed_actions: Ver todas las acciones recomendadas
       hide_proposed_actions: Ocultar acciones recomendadas
       pending_title: Pendientes
+      execute: "Marcar la acción %{name} como realizada"
+      unexecute: "Desmarcar la acción %{name} como realizada"
       show_description: Mostrar descripción
       without_pending_actions: No hay acciones recomendadas pendientes
       done_title: Realizadas