CONTRIBUTING.md: update links to golang docs and blog

- docs moved to https://go.dev/doc/
- blog moved to https://go.dev/blog/

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit b18e170631998d9fdea893d6b3961aecc65cebae)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

CONTRIBUTING.md

@@ -422,6 +422,6 @@ The rules:
     guidelines. Since you've read all the rules, you now know that.
 
 If you are having trouble getting into the mood of idiomatic Go, we recommend
-reading through [Effective Go](https://golang.org/doc/effective_go.html). The
-[Go Blog](https://blog.golang.org) is also a great resource. Drinking the
+reading through [Effective Go](https://go.dev/doc/effective_go). The
+[Go Blog](https://go.dev/blog/) is also a great resource. Drinking the
 kool-aid is a lot easier than going thirsty.