Broken link in the fittedtemplate example

[The fittedtemplate example documentation](https://www.fieldtriptoolbox.org/example/fittemplate/#method-2-on-the-basis-of-the-full-head-surface) has a broken link. I believe [this is the correct link](https://github.com/markeroon/matlab-computer-vision-routines/blob/master/third_party/CPD2/core/cpd_register.m) that contains the function used by `prepare_mesh_fittemplate`