Fix links in optimal control overview (#125)

* fix links in optimal control

* remove overview notebook to fix links for now

Author: rochisha0

tutorials-v5/optimal-control/01-optimal-control-overview.md

@@ -31,9 +31,6 @@ number of timeslots and/or total time for the evolution.
 Different initial (starting) pulse types can be tried.
 The initial and final pulses are displayed in a plot
 
-For more background on the pulse optimisation see:
-[QuTiP overview - Optimal Control](http://nbviewer.ipython.org/github/qutip/qutip-notebooks/blob/master/examples/example-optimal-control-overview.ipynb)  
-
 ```python
 import datetime