roles/nginx: enable nginx ssl_session_tickets

This has apparently been supported since nginx 1.23.2 and is safe
to use the default (on) now.

See: https://github.com/mozilla/server-side-tls/issues/284

roles/nginx/templates/https.j2

@@ -39,15 +39,6 @@
     resolver {{ nginx_ssl_stapling_resolver }};
     {% endif %} {# end: use_letsencrypt #}
 
-    # nginx does not auto-rotate session ticket keys: only a HUP / restart will do so and
-    # when a restart is performed the previous key is lost, which resets all previous
-    # sessions. The fix for this is to setup a manual rotation mechanism:
-    # http://trac.nginx.org/nginx/changeset/1356a3b9692441e163b4e78be4e9f5a46c7479e9/nginx
-    #
-    # Note that you'll have to define and rotate the keys securely by yourself. In absence
-    # of such infrastructure, consider turning off session tickets:
-    ssl_session_tickets off;
-
     {% if enable_hsts == true %}
     # Enable this if you want HSTS (recommended, but be careful)
     # Include all subdomains and indicate to Google that we want this pre-loaded in Chrome's HSTS store