[Typo] Sect 5.0, "Logging" section, minor typo "nodes" should be "node"

[mars0i]

"Logging" subsection of section 5.0:

Another example is a function that computes the sum of all the nodes in a tree with an inorder traversal, while simultaneously recording each nodes visited:

"nodes" should be "node".

[david-christiansen]

Thanks!