Uploading a VEX with "state": "exploitable" does not clear the justifiaction

### Current Behavior

Uploading a VEX that affects a finding that has already been analyzed before does not clear the justification field.

This is especially problematic if state is set to "exploitable" as no "justification" value fits that state.

### Steps to Reproduce

1. Upload a vex with analysis entry:
```
"analysis": {
"state": "not_affected",
"justification": "code_not_reachable"
}
```
2. Upload a VEX with different analysis entry for the same finding:
```
"analysis": {
"state": "exploitable"
}
```
3. Download a VEX and observe the analysis for that finding is:
```
"analysis" : {
"state" : "exploitable",
"justification" : "code_not_reachable"
},
```

### Expected Behavior

If justification is not present in VEX file it should be cleared on D-T and the value should not be present in later VEX export

### Dependency-Track Version

4.13.1

### Dependency-Track Distribution

Container Image

### Database Server

PostgreSQL

### Database Server Version

_No response_

### Browser

Mozilla Firefox

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this defect was already reported