Remove duplicate word

See gh-48874

Signed-off-by: Tran Ngoc Nhan <ngocnhan.tran1996@gmail.com>

documentation/spring-boot-docs/src/docs/antora/modules/reference/pages/io/rest-client.adoc

@@ -281,7 +281,7 @@ Instead of directly using a javadoc:org.springframework.web.client.RestClient[]
 
 HTTP Service interfaces defines a service contract by using methods that are annotated with javadoc:org.springframework.web.service.annotation.HttpExchange[format=annotation], or more typically the method specific variants (javadoc:org.springframework.web.service.annotation.GetExchange[format=annotation], javadoc:org.springframework.web.service.annotation.PostExchange[format=annotation], javadoc:org.springframework.web.service.annotation.DeleteExchange[format=annotation], etc).
 
-For example, the following code defines an HTTP Service for an an "`echo`" API that will return a JSON object containing an echo of the request.
+For example, the following code defines an HTTP Service for an "`echo`" API that will return a JSON object containing an echo of the request.
 
 include-code::EchoService[]