Fix broken example by updating draft-mcquistin-quic-augmented-diagrams-03.xml

[DaveEM]

This PR updates draft-mcquistin-quic-augmented-diagrams-03.xml to have valid content so that the first example command in README.md works. I also updated the Unpredictable Bits field to be >= 38 bits instead of > 38 bits since section 10.3 of RFC 9000 says:

"the Unpredictable Bits field needs to include at least 38 bits of data (or 5 bytes, less the two fixed bits)".