chore: Update default start date to January 1, 2040

[feanil]

Push this forward so things don't automatically in a few years for future courses.

[kdmccormick]

For posterity:

• We know this is a bad fix, but we don't have time to do the right fix, and we want to merge this now in order to reduce the number of courses that will surprise-start on 1/1/2030.
• We don't want to push it out to like 1/1/2099 because the user has to page through datepicker UI to choose a start date
• The right fix would probably involve making start nullable, or having a separate available boolean field
  • Or, defaulting the start today to (date.today() + 1 year)
• We know that a bunch of courses will start on 1/1/2030 regardless of this PR
• We discussed doing a data migration between now and 1/1/2030, which checks to see if the start date is exactly 1/1/2030 or 1/1/2040 and, if it is, changing it to like (date.today() + 5 years) and raising a warning to the operator