Sometimes you no longer need to share a resource, or you've made personal changes to a lesson that your colleagues don't need access to. Here are the simple steps to removing a lesson you've shared:
Find your lesson within Resources.
Select "Share" in the Lesson Information on the side.
In the bottom right corner of the pop up, you'll see the "Unshare" button. Click this.
Make sure to read the warning in full. If you do wish to prevent the lesson from being accessible to other teachers in the future, proceed and you're done!