BUG: Toggling multiple code editor for the preview leaves out the code editor instances

[nndda]

Describe the bug
When you open one of the preview's code editor, and then open another one in the same page, if you tries to close/toggle off any of them, the CodeMirror editor instance will not be properly destroyed.

To Reproduce
Steps to reproduce the behavior:

1. Open any of the component's documentation page
2. Toggle one of the preview's HTML + CSS editor on
3. Do that for another one
4. And then toggle one of them off

You will see that the code editor will not be destroyed properly.

Expected behavior
The code editor instance should be destroyed properly.