docs: Update README (#3177)

README.md

@@ -226,7 +226,7 @@ import "github.com/gregjones/httpcache"
 ```
 
 Learn more about GitHub conditional requests at
-https://docs.github.com/en/rest/overview/resources-in-the-rest-api#conditional-requests.
+https://docs.github.com/en/rest/using-the-rest-api/best-practices-for-using-the-rest-api?apiVersion=2022-11-28#use-conditional-requests-if-appropriate
 
 ### Creating and Updating Resources ###