Fixed a small typo in the openssl cheatsheet.

cheatsheets/openssl

@@ -9,7 +9,7 @@ openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
 
 # (The above commands may be run in sequence to generate a self-signed SSL certificate.)
 
-To view certificate expiration:
-+echo | openssl s_client -connect <hostname>:443 2> /dev/null | \
+# To view certificate expiration:
+echo | openssl s_client -connect <hostname>:443 2> /dev/null | \
 awk '/-----BEGIN/,/END CERTIFICATE-----/' | \
 openssl x509 -noout -enddate