DOC: proxy-protocol: Make example for PP2_SUBTYPE_SSL_SIG_ALG accurate

DOC: proxy-protocol: Make example for PP2_SUBTYPE_SSL_SIG_ALG accurate

The docs call out that this field is the algorithm used to
sign the certificate. However, the example only had the hash portion of
the signature algorithm. This change updates the example to be accurate
based on a value written by HAProxy, which is based on an OID for
signature algorithms. I based example on a real TLV written by
HAProxy on my machine with all SSL TLVs enabled in config.