Migration Center 26B not highlighting differences in source code

Summary:

In release 26B we are forced to use the Redwood design which is also applied to the Migration Center. When I do a migration e.g. from a development site to a test site, the differences in libraries (util libraries or Commerce libraries) aren't shown anymore when clicking on "Script". It only shows that the script has been updated and shows original and new version side by side. But it doesn't highlight the changed lines of code anymore with colors. Without this, the comparison view is useless.

How can I switch back to Classic design migration center?

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