Add sentence to elaborate on enabling travel

We recently put travel back under a beta, which means customers need to reach out to their AM or sales to get a demo before travel can be manually enabled by us (aka add them to the beta).

Just adding instructions into each to make this more clear.

Author: strepanier03

docs/articles/expensify-classic/travel/Book-With-Expensify-Travel.md

@@ -17,6 +17,8 @@ With Expensify Travel, you can:
 
 There is a flat fee of $15 per trip booked. A single trip can include multiple bookings, such as a flight, a hotel, and a car rental.
 
+Contact your Account manager or salesteam@expensify.com to get a demo of travel and have it enabled for your company.
+
 # Book travel
 
 To book travel from the Expensify web app,