[FIX] mail: html tags visible for a split second at channel creation

Before this commit:

When you create a new channel HTML tags are visible in Autocomplete text area
for a split second

After this commit:

Added prevendDefault for the autocomplete select event to stop it's defaullt
behaviour as changing the autocomplete text area's value by the selected item's
value

Task-2792365

closes odoo/odoo#88148

X-original-commit: cc11accfeca4bee0f4a364bf59b6311a99855c2b
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/models/discuss.js

@@ -34,6 +34,9 @@ registerModel({
          * @param {integer} ui.item.id
          */
         async handleAddChannelAutocompleteSelect(ev, ui) {
+            // Necessary in order to prevent AutocompleteSelect event's default
+            // behaviour as html tags visible for a split second in text area
+            ev.preventDefault();
             const name = this.addingChannelValue;
             this.clearIsAddingItem();
             if (ui.item.special) {