Do not use deprecated future cycle

It has become default some versions ago.

Issue #946
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/html/admin/performance.html

 {% extends "admin/base_site.html" %}
 {% load i18n %}
 {% load translations %}
-{% load cycle from future %}
 
 {% block title %}{% trans "Performance report" %}{% endblock %}
 

weblate/html/admin/ssh.html

 {% extends "admin/base_site.html" %}
 {% load i18n %}
-{% load cycle from future %}
 
 {% block title %}{% trans "SSH keys" %}{% endblock %}