Don't use a translucent color for cards/tables/tabs

[janfaracik]

Small one to stop using translucent colors for cards/tables/tabs. This isn't really an issue in 'core' but in the Design Library the components can look a little odd when overlaying a colorful background (the color bleeds through). There shouldn't be any differences in 'core', apart from perhaps an unnoticeable hue change.

Before

After

Testing done

• Cards/tables/tabs look as expected

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