test(a11y): low contrast for chip buttons in active state and tags

[mfranzke]

Several chips contain text that has a contrast too low regarding their background-color, like e.g. warning, poi-kunst-kultur, poi-wissenswertes and poi-zivile-rel-einrichtungen.

• https://db-ui.github.io/core/patterns/elements-chips/index.html
• https://db-ui.github.io/core/patterns/elements-tags/index.html