UX: Fix deselect text location in edit sidebar category/tag modal (#23966)

Why this change?

In 38d3208027, the position of the
`headerBelowTitle` outlet was changed causing the deselect text in the
edit sidebar catgegory/tag modals to appear inline with the title which
we do not want.

What does this change do?

This change introduces the `belowModalTitle` outlet in `DModal` which is
where the `headerBelowTitle` outlet was located before it was changed.

app/assets/javascripts/discourse/app/components/d-modal.hbs

@@ -56,6 +56,8 @@
                     {{/if}}
                   </div>
                 {{/if}}
+
+                {{yield to="belowModalTitle"}}
               </div>
 
               {{yield to="headerBelowTitle"}}

app/assets/javascripts/discourse/app/components/sidebar/edit-navigation-menu/modal.hbs

@@ -3,7 +3,7 @@
   @title={{i18n @title}}
   @closeModal={{@closeModal}}
 >
-  <:headerBelowTitle>
+  <:belowModalTitle>
     <p class="sidebar__edit-navigation-menu__deselect-wrapper">
       <DButton
         @label="sidebar.edit_navigation_modal_form.deselect_button_text"
@@ -14,7 +14,7 @@
 
       {{@deselectAllText}}
     </p>
-  </:headerBelowTitle>
+  </:belowModalTitle>
 
   <:belowHeader>
     <div class="sidebar__edit-navigation-menu__filter">