Update pleroma.nginx to support TLSv1.3

Based on SSL config from https://ssl-config.mozilla.org/

installation/pleroma.nginx

@@ -37,18 +37,17 @@ server {
 
     listen 443 ssl http2;
     listen [::]:443 ssl http2;
-    ssl_session_timeout 5m;
+    ssl_session_timeout 1d;
+    ssl_session_cache shared:MozSSL:10m;  # about 40000 sessions
+    ssl_session_tickets off;
 
     ssl_trusted_certificate   /etc/letsencrypt/live/example.tld/chain.pem;
     ssl_certificate           /etc/letsencrypt/live/example.tld/fullchain.pem;
     ssl_certificate_key       /etc/letsencrypt/live/example.tld/privkey.pem;
 
-    # Add TLSv1.0 to support older devices
-    ssl_protocols TLSv1.2;
-    # Uncomment line below if you want to support older devices (Before Android 4.4.2, IE 8, etc.)
-    # ssl_ciphers "HIGH:!aNULL:!MD5 or HIGH:!aNULL:!MD5:!3DES";
+    ssl_protocols TLSv1.2 TLSv1.3;
     ssl_ciphers "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4";
-    ssl_prefer_server_ciphers on;
+    ssl_prefer_server_ciphers off;
     # In case of an old server with an OpenSSL version of 1.0.2 or below,
     # leave only prime256v1 or comment out the following line.
     ssl_ecdh_curve X25519:prime256v1:secp384r1:secp521r1;