Fix typo causing 3rd-trimester courses not to appear

[jburns20]

On line 703 of IHWCurriculum.m, the following line:
else if ([d compare:[self.trimesterEndDates objectAtIndex:1]] != NSOrderedDescending)
should be replaced by
else if ([d compare:[self.trimesterEndDates objectAtIndex:3]] != NSOrderedDescending)

stupid copy-paste mistake :(