Update ghost.sh script expiry help text
Created by: uroboro
While the help text reads
-x <expiry> - Expiration for paste (with units: ns/us/ms/s/m/h)
Both of the following options are valid
ghost.sh -x 4d ...
ghost.sh -x 1w ...
And result in the expected expiry time of '4 days' and '1 week'.