Fix Code of Conduct link in Readme. (node-fetch#1532)

Author: Sashank999

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 Thank you for considering to contribute to `node-fetch` 💖
 
-Please note that this project is released with a [Contributor Code of Conduct][./CODE_OF_CONDUCT.md].
+Please note that this project is released with a [Contributor Code of Conduct](CODE_OF_CONDUCT.md).
 By participating you agree to abide by its terms.
 
 ## Setup