[IMP] portal_rating: remove "Published on" when updating or creating comment

When answering to a comment, or editing such an answer, the form shows
a "Published on" which is supposed to be followed by the date the comment
has been published. However, since when using the form we are editing or
creating an answer comment, it remains empty and useless. Therefore, we
remove it. It is still on comments once set, but not while editing them.

Task-2728564

Part-of: odoo/odoo#82792

addons/portal_rating/static/src/xml/portal_chatter.xml

@@ -94,7 +94,6 @@
             <div class="media-body">
                 <div class="o_portal_chatter_message_title">
                     <h5 class='mb-1'><t t-esc="rating.publisher_name"/></h5>
-                    <p>Published on <t t-esc="rating.publisher_datetime"/></p>
                 </div>
                 <textarea rows="3" class="form-control o_portal_rating_comment_input"><t t-esc="rating.publisher_comment"/></textarea>
                 <div>