authexec: migrating taps

This formula no longer works on anything newer than Lion (See #34039),
so handing it over to Misty’s Tigerbrew fork where it could still be
useful. As far as tap_migrations goes though, it's being moved to the
boneyard due to Misty's fork not technically being a 'tap'.

Closes #34348.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>