Overview ruler decorations don't disappear when the decoration is disposed of

Notice the blue outline disappears but the overview ruler doesn't get re-rendered:

![Recording 2022-03-17 at 08 57 48](https://user-images.githubusercontent.com/2193314/158841126-273a823f-4d3b-4a5d-ad7b-ded667de38cb.gif)
