Whisper only group-wide, not raid-wide.

Currently, only the people in the same group as the raid-lead will receive the whispers from Chromie when mythic mode is turned on/off. Would be nice if it could be raid wide

> Chromie whispers: We're switching to the challenging version of the history lesson now. (Mythic Mode)


> Chromie whispers: We're switching to the cinematic version of the history lesson now. (Normal mode)