Update remove-potcdate.sin from gettext-0.21
It seems we have not been updating our copies of remove-potcdate.sin when we've updated other gettext bootstrap files. That's not very serious, as the differences between our version and the latest one (from gettext-0.21) still seems to be just comments. Still, let's update our copies to match the other bootstrap files from gettext-0.21.
S2_6 seems to have these already.