update readme

Author: davidwilby

README.md

@@ -3,9 +3,6 @@
 ## Using these slides
 <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-sa/4.0/80x15.png" /></a><br />This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International License</a>.
 
-## Contributing
-I welcome contributions to these slides, please make a fork of this repository, make your changes and open a pull request against this repo.
-
 ## Rendering the slides locally
 These slides are produced using [Quarto](https://quarto.org).