Bug 22716: Use gender-neutral pronouns in system preference descriptions

Bug 22716: Use gender-neutral pronouns in system preference descriptions

This patch makes a few corrections to the .pref files which provide
descriptions for system preferences. Language like "him or her" is
replaced with "they/them" pronouns.

To test, apply the patch and check the following preferences:

 - OPACFineNoRenewalsBlockAutoRenew
 - ExpireReservesMaxPickUpDelayCharge
 - PatronSelfRegistrationVerifyByEmail

Signed-off-by: Lisette <lisettes@latahlibrary.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>