Remove tls1.1 in notary

Signed-off-by: DQ <dengq@vmware.com>

make/photon/prepare/templates/nginx/notary.server.conf.jinja

@@ -6,7 +6,7 @@
     ssl_certificate_key {{ssl_cert_key}};
   
     # recommendations from https://raymii.org/s/tutorials/strong_ssl_security_on_nginx.html
-    ssl_protocols tlsv1.1 tlsv1.2;
+    ssl_protocols tlsv1.2;
     ssl_ciphers '!aNULL:kECDH+AESGCM:ECDH+AESGCM:RSA+AESGCM:kECDH+AES:ECDH+AES:RSA+AES:';
     ssl_prefer_server_ciphers on;
     ssl_session_cache shared:ssl:10m;