Table formatting broken in dark mode

[plaa]

Describe the change

If the browser is in dark mode, the background of tables are partially white, making the text unlegible.

For example at https://w3c.github.io/aria/#alert browsing with Chrome with dark mode:

Link to the version of the specification or documentation you were looking at

Link to documentation: https://w3c.github.io/aria/#alert

Does the issue exists in the editors draft (the editors draft is the most recent draft of the specification)? Yes

[pkra]

Duplicate of #2429, #2397, #2398, #2400 etc.

Will be fixed via #2410