Update README.md so openssl command is easier to copy-paste

This changes the line `openssl x509 -in path/to/cert.pem -nameopt RFC2253 -subject -noout` to put the `-in` parameter at the end of the line, so that it's easier to ^W the path and replace it with my own.

Tested that this works with OpenSSL 3.1.6 4 Jun 2024 (Library: OpenSSL 3.1.6 4 Jun 2024) and OpenSSL 3.3.0 9 Apr 2024 (Library: OpenSSL 3.3.0 9 Apr 2024) on an Ubuntu 22.04.4 container and MacOS 14.7.1

Author: ecdaero

deps/rabbitmq_auth_mechanism_ssl/README.md

@@ -54,7 +54,7 @@ produced by OpenSSL's "-nameopt [RFC 2253"](https://tools.ietf.org/html/rfc2253)
 You can obtain this string form from a certificate with a command like:
 
 ```
-openssl x509 -in path/to/cert.pem -nameopt RFC2253 -subject -noout
+openssl x509 -nameopt RFC2253 -subject -noout -in path/to/cert.pem
 ```
 
 or from an existing amqps connection with commands like: