grafana: Limit cookies to HTTPS

Signed-off-by: Florian Pritz <bluewind@xinu.at>

roles/grafana/templates/grafana.ini.j2

@@ -175,7 +175,7 @@ admin_user = admin
 ;disable_brute_force_login_protection = false
 
 # set to true if you host Grafana behind HTTPS. default is false.
-;cookie_secure = false
+cookie_secure = true
 
 # set cookie SameSite attribute. defaults to `lax`. can be set to "lax", "strict" and "none"
 ;cookie_samesite = lax