When inserting/editing a code sample in Tiny, the text within the code blocks can have a poor colour contrast against the greyish background.

To reproduce:

1. Restore the example course backup CodeExamplesBackup.mbz.
2. Go to the restored course, turn the editing mode on and edit the settings for the "Code examples in different languages".
3. You should see the code blocks displayed on the Tiny editor.
4. Run axe DevTools on the page.
5. Expected: There are no errors related to colour contrast.
6. Actual: There's a bunch of errors related to colour contrast.