Add UnnecessaryParentReference to README ToC

The UnnecessaryParentReference exists in the document but not in
the table of contents.

Change-Id: I14a08a2cd4a1681388c29922964d8c787fed7fd6
Reviewed-on: http://gerrit.causes.com/44876
Reviewed-by: Joe Lencioni <joe.lencioni@brigade.com>
Tested-by: jenkins <jenkins@brigade.com>