Update graffiti type

Author: courtneyeh

validator/client/src/main/java/tech/pegasys/teku/validator/client/restapi/apis/GetGraffiti.java

@@ -44,6 +44,9 @@ public class GetGraffiti extends RestApiEndpoint {
       DeserializableTypeDefinition.string(Bytes32.class)
           .formatter(GetGraffiti::processGraffitiString)
           .parser(Bytes32Parser::toBytes32)
+          .example("Example graffiti")
+          .description("Bytes32 string")
+          .format("byte")
           .build();
 
   private static final SerializableTypeDefinition<GraffitiResponse> GRAFFITI_RESPONSE_TYPE =

validator/client/src/test/resources/tech/pegasys/teku/validator/client/restapi/schema/GraffitiResponse.json

@@ -11,7 +11,10 @@
           "$ref" : "#/components/schemas/Pubkey"
         },
         "graffiti" : {
-          "type" : "string"
+          "type" : "string",
+          "description" : "Bytes32 string",
+          "example" : "Example graffiti",
+          "format" : "byte"
         }
       }
     }