Reduce memcached memory for archwiki

The arch wiki box previously had plenty of ram to play around with, but
the current box is significantly smaller. Memcached seems to cache ~ 600
MB on average so 1024 should suit us fine.

roles/archwiki/defaults/main.yml

@@ -9,7 +9,7 @@ archwiki_question_answer_file: '/srv/http/archwiki/registration-question-answer.
 
 archwiki_socket: '/run/php-fpm7/archwiki.socket'
 archwiki_memcached_socket: '/run/memcached/archwiki.sock'
-archwiki_memcached_memory: 2048
+archwiki_memcached_memory: 1024
 
 archwiki_db: 'archwiki'
 archwiki_db_host: 'localhost'