Refine Add code task copy

What does this MR do and why?

This Learn GitLab step gets completed regardless of how someone adds code (not limited to WebIDE). As such we should update the copy to be more accurate.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK
• Visit /users/sign_up. Submit the form.
• On welcome page select Just me and Create a new project.
• Submit the form.
• Enter group and project name. Finish registration.

Related to #434238 (closed)