tail: retire -h flag

[mknos]

• The standard tail command doesn't support -h [1]
• GNU and OpenBSD versions print "unknown option" error
• With this patch, usage string is printed after the error, which matches OpenBSD version
• Simplify usage() so it only takes a single (optional) error message param

1. https://pubs.opengroup.org/onlinepubs/007908799/xcu/tail.html

[briandfoy]

changes: remove the -h option to be consistent with GNU / BSD