fix outdate url

maoyangLiu · maoyangLiu · commit 60dda15ce53c · 2021-03-18T19:58:11.000+08:00
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -1 +1 @@
-This document has moved to https://minikube.sigs.k8s.io/docs/contributing/guide/
+This document has moved to https://minikube.sigs.k8s.io/docs/contrib/

Original file line number	Diff line number	Diff line change
`@@ -1 +1 @@`
`1`		`-This document has moved to https://minikube.sigs.k8s.io/docs/contributing/guide/`
	`1`	`+This document has moved to https://minikube.sigs.k8s.io/docs/contrib/`