Calling `.after` on a dateutil.rrule object that has an UNTIL clause
performs very poorly if the interval is low and the start time is a long
time ago. This patch replaces two test cases where we were using a
minute interval with a fixed start time of (currently) 2 years ago,
which resulted in aproximately 40s of execution time to simply evaluate
`.after(now())`. Replacing these two tests with tests that start from
"yesterday" while keeping the same INTERVAL and UNTIL settings
eliminates this unnecessary slowdown while maintaining the spirit of the
original tests.