docs: Correct variable name in rate limit error logging example (#3902)

Author: bmeverett

README.md

@@ -214,8 +214,8 @@ To detect a primary API rate limit error, you can check if the error is a
 ```go
 repos, _, err := client.Repositories.List(ctx, "", nil)
 var rateErr *github.RateLimitError
-if errors.As(err, &rateError) {
-	log.Printf("hit primary rate limit, used %v of %v\n", rateErr.Rate.Used, rateErr.rate.Limit)
+if errors.As(err, &rateErr) {
+	log.Printf("hit primary rate limit, used %v of %v\n", rateErr.Rate.Used, rateErr.Rate.Limit)
 }
 ```