[FIX] mail: scrollbar for emoji

Open discuss on mobile phone, click on the smiley icon, not all smileys
are visible on screen.

opw-2030315

closes odoo/odoo#35146

Signed-off-by: Julien Castiaux <Julien00859@users.noreply.github.com>

addons/mail/static/src/scss/composer.scss

@@ -207,6 +207,8 @@
             .o_mail_emoji_container {
                 @include o-position-absolute(auto, 0, 100%, 0);
                 border-bottom-width: 1px;
+                max-height: calc(100vh - 100%);
+                overflow-y: auto;
             }
         }
         .o_composer_input {