fix(#651): fix incorrect assignment

the same variable was assigned twice accidentally

Author: BlasiusSecundus

graphql-spring-boot-autoconfigure/src/main/java/graphql/kickstart/autoconfigure/web/servlet/GraphQLWebAutoConfiguration.java

@@ -316,7 +316,7 @@ public GraphQLConfiguration graphQLServletConfiguration(
         .asyncTimeout(asyncTimeout)
         .with(asyncTaskDecorator)
         .asyncCorePoolSize(asyncServletProperties.getThreads().getMin())
-        .asyncCorePoolSize(asyncServletProperties.getThreads().getMax())
+        .asyncMaxPoolSize(asyncServletProperties.getThreads().getMax())
         .with(asyncExecutor)
         .build();
   }