[REM] website_slides : remove deprecated enroll route

Removes the route slides/channel/enroll, (slides_channel_join_http method).
The attendees are enrolled in front-end through slides/channel/join,
used in different places through the Join channel button and javascript.
The old route is not used anymore.

Task-2508019
COM PR - odoo/odoo#70291

addons/website_slides/controllers/main.py

@@ -660,14 +660,6 @@ class WebsiteSlides(WebsiteProfile):
 
         return values
 
-    @http.route('/slides/channel/enroll', type='http', auth='public', website=True)
-    def slide_channel_join_http(self, channel_id):
-        # TDE FIXME: why 2 routes ?
-        if not request.website.is_public_user():
-            channel = request.env['slide.channel'].browse(int(channel_id))
-            channel._action_add_member()
-        return request.redirect("/slides/%s" % (slug(channel)))
-
     @http.route(['/slides/channel/join'], type='json', auth='public', website=True)
     def slide_channel_join(self, channel_id):
         if request.website.is_public_user():