Update README.

Author: OlgaMaciaszek

docs/src/main/asciidoc/README.adoc

@@ -1,4 +1,4 @@
-image::https://github.com/spring-cloud/spring-cloud-openfeign/actions/workflows/maven.yml/badge.svg?branch=4.1.x&style=svg[https://github.com/spring-cloud/spring-cloud-openfeign/actions/workflows/maven.yml/badge.svg?branch=4.1.x&style=svg[https://github.com/spring-cloud/spring-cloud-openfeign/workflows/Build/badge.svg?branch=main&style=svg]["Build",link="https://github.com/spring-cloud/spring-cloud-openfeign/actions"]
+image::https://github.com/spring-cloud/spring-cloud-openfeign/actions/workflows/maven.yml/badge.svg?branch=4.2.x&style=svg[https://github.com/spring-cloud/spring-cloud-openfeign/actions/workflows/maven.yml/badge.svg?branch=4.2.x&style=svg[https://github.com/spring-cloud/spring-cloud-openfeign/workflows/Build/badge.svg?branch=main&style=svg]["Build",link="https://github.com/spring-cloud/spring-cloud-openfeign/actions"]
 
 WARNING: As announced in https://spring.io/blog/2022/12/16/spring-cloud-2022-0-0-codename-kilburn-has-been-released#spring-cloud-openfeign-feature-complete-announcement[Spring Cloud 2022.0.0 release blog entry], we're now treating the Spring Cloud OpenFeign project as feature-complete. We are only going to be adding bugfixes and possibly merging some small community feature PRs. We suggest migrating over to https://docs.spring.io/spring-framework/reference/integration/rest-clients.html#rest-http-interface[Spring Interface Clients] instead.