Fixed type in documentation related to custom filters

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -1532,7 +1532,7 @@ public class PreGatewayFilterFactory extends AbstractGatewayFilterFactory<PreGat
 		// grab configuration from Config object
 		return (exchange, chain) -> {
             //If you want to build a "pre" filter you need to manipulate the
-            //request before calling change.filter
+            //request before calling chain.filter
             ServerHttpRequest.Builder builder = exchange.getRequest().mutate();
             //use builder to manipulate the request
             return chain.filter(exchange.mutate().request(request).build());