B+ Trees Update Internal Nodes

[ClarkFall55]

To reproduce:

1. Go to the B+ tree visualizer
2. Put nodes in the tree to make it look like this (the link should do this for you):

3. Delete 30 as shown.
4. Notice that the root value changed from 30 to 40 despite the fact that internal node values should not be changed (only added or deleted) unless borrowing, which did not happen here.