Change the accessible role of info boxes to `note` (#2022)

The `alert` role is intrusive and should only be used when the user's immediate attention is required.

Given that this boxes only provide additional content to the current paragraph,
the `note` role seems more appropriate.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

changelogs/internal/newsfragments/2022.clarification

@@ -0,0 +1 @@
+Change the accessible role of info boxes to `note`.

layouts/partials/alert.html

@@ -15,6 +15,6 @@
 {{ $content := .content}}
 {{ $omit_title := .omit_title }}
 
-<div class="alert {{ $type }} {{ if $omit_title }}omit-title{{end}}" role="alert">
+<div class="alert {{ $type }} {{ if $omit_title }}omit-title{{end}}" role="note">
 {{ $content }}
 </div>