Fix a compilation problem in the SmallRye GraphQL guide

docs/src/main/asciidoc/smallrye-graphql.adoc

@@ -721,17 +721,18 @@ public class Film implements SearchResult {
     // ...
 }
 
-public class Hero implements Character, SearchResult {
+public interface Character implements SearchResult {
     // ...
 }
 
-public class Ally implements Character, SearchResult {
+public class Hero implements Character {
     // ...
 }
-----
 
-TIP: We can also leverage inheritance and have `interface Character extends SearchResult`.
-This will result in all implementations of `Character` being added as members of the `SearchResult` union in the schema.
+public class Ally implements Character {
+    // ...
+}
+----
 
 Update `GalaxyService` to provide search: