[experiment-next] Remove leaveNode() calls on AbstractImmutableNodeTraverser

[samsonasik]

@TomasVotruba this is continue of PR:

• [experiment] Remove leaveNode() method on AbstractRector and CallableNodeVisitor #7767

since leaveNode() method removed on AbstractRector, I think the leaveNode() calls can be removed from AbstractImmutableNodeTraverser

[samsonasik]

@TomasVotruba ready 👍

[TomasVotruba]

Seems good to me. The leaveNode() in AbstractRector should be marked as final to avoid override. Not just docblock, but natively.
Just in case someone would try to use it, so it's not skipped silent.y

[samsonasik]

The leaveNode already removed from AbstractRector, do you mean I need to add leaveNode method back to AbstractRector ?