remove nickname from MyFamily man page section

This is originally from https://trac.torproject.org/projects/tor/ticket/22223#comment:6

but it is still in the man page as of 0.4.2.6

Please remove this phrase from the tor man page

    When listing a node, it's better to list it by fingerprint than by
    nickname: fingerprints are more reliable.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information