Update Generated Samples

Signed-off-by: Chrimle <28791817+Chrimle@users.noreply.github.com>

Author: Chrimle

samples/client/petstore/java/okhttp-gson-3.1/src/main/java/org/openapitools/client/model/AllOfSimpleModel.java

@@ -165,10 +165,7 @@ public String toString() {
    * (except the first line).
    */
   private String toIndentedString(Object o) {
-    if (o == null) {
-      return "null";
-    }
-    return o.toString().replace("\n", "\n    ");
+    return String.valueOf(o).replace("\n", "\n    ");
   }