archweb: limit to 10 requests / second

In reality the uwsgi endpoint gets hit with only 1 request on a normal
page load so 20 requests is way to lenient.

roles/archweb/templates/nginx.d.conf.j2

 # limit rss requests to 1 r/m
 limit_req_zone $binary_remote_addr zone=rsslimit:8m rate=1r/m;
 
-# limit general requests to 20 r/s to block DoS attempts.
-limit_req_zone $binary_remote_addr zone=archweblimit:10m rate=20r/s;
+# limit general requests to 10 r/s to block DoS attempts.
+limit_req_zone $binary_remote_addr zone=archweblimit:10m rate=10r/s;
 
 limit_req_status 429;