Remove CSS for cell output scroll for MyST-NB

[choldgraf]

Context

MyST-NB is starting to bring in more CSS rules into its own package so that they are self-contained. We should remove MyST-NB rules from this package so that they aren't duplicated (at least unless we intentionally want the behavior to be different)

Proposal

Here's the PR that adds the lines to MyST-NB - we should basically remove the respective lines from this package:

• BUG: Adding scroll bars with proper cell tags MyST-NB#454

Tasks and updates

No response

[dprada]

As a user, I found intuitive the fact that I could scroll the cell's output with MyST-NB. I was probably wrong, maybe this is only explicitly written in the Jupyter Book documentation and not in MyST-NB... But that was intuition.

I am using MyST-NB with sphinx to write the documentation of a scientific python library, and I find MyST-NB extremely useful.
Maybe a custom style of the scroll bar should be included in the theme, but not the fact that these cell tags are functional.

Anyway, thanks a lot for keeping and developing these tools. 👍🏻