Throw CannotResolveClassException: OpenModelThreadGroup when I use SaveService.loadTree() method load the jmx file.

### Expected behavior

I hope use SaveService.loadTree() load contain OpenModelThreadGroup jmx file,but it throw CannotResolveClassException

### Actual behavior

throw CannotResolveClassException

### Steps to reproduce the problem

1. use jemter gui create a jmx script file it contain OpenModelThreadGroup feature
2. use java program invoke SaveService.loadTree() method load the jmx file
``` HashTree hashTree = SaveService.loadTree(scriptFile);```
4. throw Exception
java.lang.IllegalArgumentException: Problem loading XML from:'/Users/m/git/service/6760ea60488693106d67df19.jmx'.
Cause:
CannotResolveClassException: OpenModelThreadGroup

Detail:com.thoughtworks.xstream.converters.ConversionException:
Debugging information
cause-exception : com.thoughtworks.xstream.converters.ConversionException
cause-message :
first-jmeter-class : org.apache.jmeter.save.converters.HashTreeConverter.unmarshal(HashTreeConverter.java:66)
class : org.apache.jmeter.save.ScriptWrapper
required-type : org.apache.jmeter.save.ScriptWrapper
converter-type : org.apache.jmeter.save.ScriptWrapperConverter
path : /jmeterTestPlan/hashTree/hashTree/OpenModelThreadGroup
line number : 10
version : 5.6.3
at org.apache.jmeter.save.SaveService.readTree(SaveService.java:456)
at org.apache.jmeter.save.SaveService.loadTree(SaveService.java:429)

### JMeter Version

5.6.3

### Java Version

8

### OS Version

mac 14.6.1