Replace usages of "M W F" with "Mon, Wed, Fri"

[JasonFreeberg]

Would be a helpful method in places where we have the real estate. UCSB uses "MTWRF", but I imagine other universities do not use this convention, so the 3-character abbreviation will make more sense to a larger audience.

https://github.com/crunch-time/crunchtime/blob/main/frontend/src/components/util/event-methods.js#L119-L155