use assertion instead of errors.As

Signed-off-by: sivchari <shibuuuu5@gmail.com>

Author: sivchari

cmd/clusterctl/client/repository/repository_github.go

@@ -319,7 +319,7 @@ func (g *gitHubRepository) getVersions(ctx context.Context) ([]string, error) {
 		if listReleasesErr != nil {
 			retryError = g.handleGithubErr(listReleasesErr, "failed to get the list of releases")
 			// Return immediately if we are rate limited.
-			if errors.As(listReleasesErr, &rateLimitError) {
+			if _, ok := listReleasesErr.(*github.RateLimitError); ok {
 				return false, retryError
 			}
 			return false, nil
@@ -384,7 +384,7 @@ func (g *gitHubRepository) getReleaseByTag(ctx context.Context, tag string) (*gi
 				return false, retryError
 			}
 			// Return immediately if we are rate limited.
-			if errors.As(getReleasesErr, &rateLimitError) {
+			if _, ok := getReleasesErr.(*github.RateLimitError); ok {
 				return false, retryError
 			}
 			return false, nil