Sign-up flow alterations

Created by: rrhyne

Marketing is altering the sign-up flow to better support self-hosted installations alongside cloud sign-ups based on user requirements.

The ask from us will be:

• Change the sign-up button to "Get started"
• Change the route to the new https://about.sourcegraph.com/get-started link (with a UTM parameter to aid tracking)
• Change other locations in the product (tour, etc) that link to sign-up to read "Get started" and the proper route

The timeframe for this will be after marketing makes these updates. It will happen either in a few days, or after the 27th of January, depending on the content platform team's development timeline.