Don't use custom theme color yellow for severity cards, to avoid clashing with Tailwind's yellow palette.

[MichaelBurgess]

We currently have a theme colour yellow, which is used for the severity cards. We're not using any tailwind yellow colours in the CLI dashboard UI, but in Steampipe Cloud we use some yellow theme colours and if we try to include yellow into the theme, this overwrites the yellow family.

I propose we renamed this themed colour to severity to avoid any downstream issues such as this.