popovers: Drop text for historical messages from three-dot menu.

Dropped text "(Message sent when you were not subscribed)" for
historical messages in the three-dot message menu.

This information was already available via the "You subscribed" type
divider lines, which were added about the same time back in 2013, and
this text feels somewhat ugly.

Also removed the historical field from the args object that is
passed to the template, as this is not used anymore.

Fixes #23198.

static/js/popovers.js

@@ -606,7 +606,6 @@ export function toggle_actions_popover(element, id) {
 
         const args = {
             message_id: message.id,
-            historical: message.historical,
             stream_id: message.stream_id,
             editability_menu_item,
             move_message_menu_item,

static/templates/actions_popover_content.hbs

@@ -131,8 +131,4 @@
             <i class="fa fa-link" aria-hidden="true"></i> {{t "Copy link to message" }}
         </a>
     </li>
-
-    {{#if historical}}
-    <li class="small">({{t "Message sent when you were not subscribed" }})</li>
-    {{/if}}
 </ul>