Update string to indicate that accounts with channels cannot be deleted

Author: marcellamaki

contentcuration/contentcuration/frontend/settings/pages/Account/index.vue

@@ -197,7 +197,7 @@
       completelyDeleteAccountLabel: 'Completely remove your account from Kolibri Studio',
       unableToDeleteAdminAccount: 'Unable to delete an admin account',
       handleChannelsBeforeAccount:
-        'You must delete these channels manually or invite others to edit them before you can delete your account.',
+        'You cannot delete accounts that have channels. You must delete these channels manually before you can delete your account.',
 
       // API strings
       apiTokenHeading: 'API Token',