Add clarity to expenses for meetups

Why is this change being made?

Having the expense policy split into two lines created confusion with an organizer as to whether the budget was $500 for food and $500 for other costs or $500 for all costs. This MR condenses the policy into a single line for clarity. Also emphasizes why it is important to keep costs low for meetups.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what