sysutils/squashfs-tools: the port had been updated to version 4.6.1

This release fixes race condition which can cause corruption of the
"fragment table" (regression introduced in August 2022) and several
bugs with the extended attributes code.

On the port's side, garbage-collect patches merged upstream, follow
HTTP/1.1 301 Moved Permanently redirection in the WWW line, and add
missing dependency on `misc/help2man' so that manpages are properly
generated against configured compressors (selected options).