[FIX] website_slides: HttpCase should be post_install

Since odoo/odoo@8d5da6e4be05 HttpCase should not be started at install.

closes odoo/odoo#39719

Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>

addons/website_slides/tests/test_ui_wslides.py

@@ -51,7 +51,7 @@ class TestUi(tests.HttpCase):
             login=user_portal.login)
 
 
-@tests.common.tagged('external', '-standard')
+@tests.common.tagged('external', 'post_install', '-standard', '-at_install')
 class TestUiYoutube(tests.HttpCase):
 
     def test_course_member_yt_employee(self):