Bug #51096 - Remove unnecessary ? for first/last day of

 > From https://bugs.php.net/bug.php?id=51096 :
 >
 > [2010-03-09 09:49 UTC] derick@php.net
 > Re-opening because of the question marks:
 > 
 > firstdayof = 'first day of'?;
 > lastdayof = 'last day of'?;
 > 
 > It shouldn't cause an issue though, but it needs fixing.

This PR fixes those unnecessary question marks. There is no behaviour change, and no tests get broken.