Update 10.4.md

[natjms]

The original solution seems to treat the argument as both a node and the complete tree, and the way its used is inconsistent with how a binary tree is defined in 10.4. This modification introduces a PRINT-BINARY-TREE-AUX following the same form of the original solution, except that the argument is explicitly a node and not a binary tree.

Complete new solution:

PRINT-BINARY-TREE(T)
    PRINT-BINARY-TREE-AUX(T.root)

PRINT-BINARY-TREE-AUX(node)
    if node != NIL
        PRINT-BINARY-TREE-AUX(node.left)
        print node.key
        PRINT-BINARY-TREE-AUX(node.right)

[walkccc]

Thank you!