[FIX] web: clear form button box before an alert

On the user form view, just after the button box, there might be an
alert component. Since BS4, this alert goes over the floating button
box in community. Before BS4, the button box went over the alert (so it
was functional but still ugly).

This commit adds an extra style for community only: clear the button
box before an alert component.

Closes https://github.com/odoo/odoo/issues/27435

closes odoo/odoo#27566

addons/web/static/src/scss/form_view_extra.scss

@@ -33,6 +33,7 @@
         width: 400px;
         text-align: right;
         float: right;
+        margin-bottom: 4px;
 
         &, & + .oe_avatar {
             + .oe_title {
@@ -40,6 +41,10 @@
             }
         }
 
+        + .alert {
+            clear: both;
+        }
+
         .oe_stat_button {
             color: $o-main-text-color;
             text-align: left;