Update README.md (#53)

The copilot trial duration was changed to 30 days in April.

Author: iamcjwilliams

README.md

@@ -28,7 +28,7 @@ GitHub Copilot can help you code by offering autocomplete-style suggestions. You
 - **Who this is for**: Developers, DevOps Engineers, Software development managers, Testers.
 - **What you'll learn**: How to install Copilot into a Codespace, accept suggestions from code, accept suggestions from comments.
 - **What you'll build**: Javascript files that will have code generated by Copilot AI for code and comment suggestions.
-- **Prerequisites**: To use GitHub Copilot you must have an active GitHub Copilot subscription. Sign up for 60 days free [Copilot](https://github.com/settings/copilot).
+- **Prerequisites**: To use GitHub Copilot you must have an active GitHub Copilot subscription. Sign up for 30 days free [Copilot](https://github.com/settings/copilot).
 - **Timing**: This course can be completed in under an hour.
 
 ### How to start this course