Fix GitHub docs links (#2039)

github/doc.go

@@ -112,7 +112,7 @@ To detect an API rate limit error, you can check if its type is *github.RateLimi
 	}
 
 Learn more about GitHub rate limiting at
-https://docs.github.com/en/free-pro-team@latest/rest/reference/#rate-limiting.
+https://docs.github.com/en/free-pro-team@latest/rest/overview/resources-in-the-rest-api#rate-limiting.
 
 Accepted Status
 
@@ -138,7 +138,7 @@ instead designed to work with a caching http.Transport. We recommend using
 https://github.com/gregjones/httpcache for that.
 
 Learn more about GitHub conditional requests at
-https://docs.github.com/en/free-pro-team@latest/rest/reference/#conditional-requests.
+https://docs.github.com/en/free-pro-team@latest/rest/overview/resources-in-the-rest-api#conditional-requests.
 
 Creating and Updating Resources