Can't mention @Copilot

[it33_mattermost (It33)]

Expected:

• When I mention @Copilot in a channel, auto-complete for mention is available, especially after it’s responded to me.

Observed:

• No auto-complete of mention for @copilot. Instead, I have to mention @ai, which doesn’t have auto-complete enabled.

[matthewbirtch]

Jira ticket created: [MM-61150] - Mattermost