wayland: Don't send proximity_in for new resources

Mutter sends a proximity-in event before the required tablet tool resource is properly allocated on the client. This is violating the Wayland protocol. Because libwayland ignores events for objects it doesn't know yet, this is not noticeable in most applications. However, if https://gitlab.freedesktop.org/wayland/wayland/-/issues/176 gets fixed, these applications would likely crash immediately. Therefore this PR removes the responsible code which, again, shouldn't have any effect on client applications as they ignore this event anyway.