Functional members are not ignored when the NotificationClient is computing the room displayName

[bmarty]

Functional members are not ignored when the NotificationClient is computing the room displayName

For Alice to reproduce the issue:

• Alice has a dm with Bob
• Alice invite a new member, Charlie
• Let Charlie be a functional member
• The room name is correct in the room list of Alice: "Bob", i.e. the functional member is not taken into account. This is expected.
• Alice receives a message (from Bob or Charlie) in this room
• The Notification Client is providing a NotificationRoomInfo.displayName which contains the name of the functional member: "Charlie, Bob"

This is not correct, the displayName should be "Bob".

[manuroe]

It seems that #4335 did not cover the push notification case.