link in preface points to old repo

[NickleDave]

Hi @poldrack

Very minor issue and you might be aware of this already but I just noticed this link in the preface still points to the old repo

statsthinking21-core/index.Rmd

Line 60 in 232ca6a

This book is meant to be a living document, which is why its source is available online at [https://github.com/poldrack/psych10-book](https://github.com/poldrack/psych10-book). If you find any errors in the book or want to make a suggestion for how to improve it, please open an issue on the Github site. Even better, submit a pull request with your suggested change.

(Guessing you want it to point here instead)