bots: Do not allow removing owner from UI.

This commit removes the "Remove owner" button
from bot-edit form since we anyways do not allow
to remove owner in the API.

Fixes #20116.

static/templates/settings/admin_bot_form.hbs

@@ -5,8 +5,7 @@
             <label for="bot_owner_select">{{t "Owner" }}</label>
             {{> dropdown_list_widget
               widget_name="edit_bot_owner"
-              list_placeholder=(t 'Filter users')
-              reset_button_text=(t '[Remove owner]')}}
+              list_placeholder=(t 'Filter users')}}
         </div>
         <div class="name_change_container">
             <label for="full_name">{{t "Full name" }}</label>