[FIX] website_forum: no auto subscription

Remove forum creator as follower of the forum. Indeed this means that generally
the website admin will be follower of all posts of this forum. Which is
probably not really necessary.

addons/website_forum/models/forum.py

@@ -157,7 +157,7 @@ class Forum(models.Model):
 
     @api.model
     def create(self, values):
-        return super(Forum, self.with_context(mail_create_nolog=True)).create(values)
+        return super(Forum, self.with_context(mail_create_nolog=True, mail_create_nosubscribe=True)).create(values)
 
     @api.model
     def _tag_to_write_vals(self, tags=''):