Revert "Avoid hard-coding ciphers into configuration (#122)" (#170)

This reverts commit fc79d23ad0.

Running-Mastodon/Production-guide.md

@@ -35,7 +35,8 @@ server {
   server_name example.com;
 
   ssl_protocols TLSv1.2;
-  ssl_ciphers HIGH:!MEDIUM:!LOW:!aNULL:!NULL:!SHA1;
+  ssl_ciphers EECDH+AESGCM:EECDH+AES;
+  ssl_ecdh_curve prime256v1;
   ssl_prefer_server_ciphers on;
   ssl_session_cache shared:SSL:10m;