Correct code of conduct link.

Author: tannewt

CONTRIBUTING.md

@@ -1,7 +1,7 @@
 Please note that this project is released with a Contributor Code of
 Conduct. By participating in this project you agree to abide by its terms.
 
-A copy is available in (CODE_OF_CONDUCT.md)[CODE_OF_CONDUCT.md].
+https://github.com/adafruit/micropython/blob/master/CODE_OF_CONDUCT.md
 
 When reporting an issue and especially submitting a pull request, please
 make sure that you are acquainted with Contributor Guidelines: