Message divider high contrast

[mcoker]

https://www.figma.com/design/iT76DS020Ry1Wswfc0Hmes/branch/wKcOq7IrzfL1gEK2mocd6r/High-Contrast-Exploration?m=auto&node-id=12395-65158&t=jKsaTsEZEFafqifW-1

[rebeccaalpert]

@lboehling - I'm fairly sure this is already inheriting these (see https://staging.patternfly.org/patternfly-ai/chatbot/messages#message-dividers) - do you want any other changes here?

[rebeccaalpert]

Closed after talking to Lucia - inheriting style.