[FIX] website_event_{meet, track_exhibitor}: fix the layout of the "Join Later" modal

Fix the layout of the "Join Later" modal. Improve the message when we can not
join an exhibitor.

Task ID-2204364
COM odoo/odoo#57022
ENT odoo/enterprise#13984
UPG odoo/upgrade#1897

addons/website_event_exhibitor/views/event_exhibitor_templates_page.xml

@@ -49,7 +49,8 @@
                         t-options="{'format': 'medium'}"/> (<t t-esc="sponsor.event_id.date_tz"/>).
                 </span>
                 <br/>
-                <span>Join us there to meet <b t-esc="sponsor.partner_name"/> !</span>
+                <span t-if="is_event_user">Attendees will be able to join to meet <b t-esc="sponsor.partner_name"/> .</span>
+                <span t-else="">Join us there to meet <b t-esc="sponsor.partner_name"/> !</span>
             </div>
         </t>
         <!-- SPONSOR JITSI + CLOSED/FULL ALERTS -->

addons/website_event_meet/views/event_meet_templates_list.xml

@@ -55,7 +55,7 @@
 </template>
 
 <template id="meeting_room_card" name="Meeting Room Card">
-    <div class="modal o_join_later_modal" t-attf-id="o_join_later_modal_#{meeting_room.id}" tabindex="-1" role="dialog" style="height: 400px; top:calc(50% - 200px);">
+    <div class="modal o_join_later_modal fixed-top" t-attf-id="o_join_later_modal_#{meeting_room.id}" tabindex="-1" role="dialog" style="top: 0">
         <div class="modal-dialog" role="document">
             <div class="modal-content">
                 <div class="mt-4 col-12 alert alert-warning text-center" role="alert">