Remove room member highlight on click

Previously it was possible to keep clicking and highlighting each member
which doesn't make any sense. We could make this exclusive by having it
highlight only when index == currentIndex, but honestly it doesn't need
to be highlighted at all. Clicking on a room member opens their user
card, there's no persistent state the user needs to keep track of here.

src/qml/RoomInformation.qml

@@ -218,7 +218,6 @@ QQC2.ScrollView {
             KeyNavigation.backtab: index === 0 ? userList.headerItem.userListSearchField : null
 
             onClicked: {
-                userDelegate.highlighted = true;
                 RoomManager.resolveResource(userDelegate.userId, "mention");
             }