fix "how many answer" always treated as plural

This fixes single persons replying "We want to be there by {stardate}"

Same type of bug as in #2622-#2624. 

I've noticed it in gameplay, but didn't realize it was unrelated to #2623 (which also confuses "single" person with "group"), until I saw it today in the code.

I've also checked through both DeliverPackage, and Taxi missions to see if there were any more of thises bugs, but I think that should be it. Other scripts seem to not have been written in that way