PointerConstraint: remove overly tight assert 2

This is a second copy of the same assert that was removed in the last
commit. It should have been removed by that commit as well but was
overlooked.

(cherry picked from commit 680cb8ef69)

river/PointerConstraint.zig

@@ -73,7 +73,6 @@ pub fn maybeActivate(constraint: *PointerConstraint) void {
     const seat: *Seat = @ptrFromInt(constraint.wlr_constraint.seat.data);
 
     assert(seat.cursor.constraint == constraint);
-    assert(seat.wlr_seat.keyboard_state.focused_surface == constraint.wlr_constraint.surface);
 
     if (constraint.state == .active) return;