[BUG] Multiple mentions items in a message triggers React missing key error

[gavinbarron]

To repro:

Have a chat message with multiple mention items, either by mentioning multiple people, or by mentioning a user in the Teams client using their full name.

Have dev tools open when you open the chat with the chat message in it.

Observe "Warning: Each child in a list should have a unique "key" prop" as an error in the console.