Fix incorrect maven property (#1561)

Author: viniciusxyz

guides/micronaut-openapi-generator-server/micronaut-openapi-generator-server.adoc

@@ -206,7 +206,7 @@ Enable the Micronaut OpenAPI server generation in your `pom.xml` file, configure
 .pom.xml
 ----
 <properties>
-    <micronaut.openapi.generate.server>true</micronaut.openapi.generate.client> <!--1-->
+    <micronaut.openapi.generate.server>true</micronaut.openapi.generate.server> <!--1-->
     <micronaut.openapi.definition>src/main/resources/library-definition.yml</micronaut.openapi.definition> <!--2-->
     <micronaut.openapi.api.package.name>micronaut.example.api</micronaut.openapi.api.package.name> <!--3-->
     <micronaut.openapi.model.package.name>micronaut.example.model</micronaut.openapi.model.package.name> <!--4-->