Max Tokens config does not appear for gemini-2.5-flash (non-thinking); it should

### App Version

v3.14.3

### API Provider

GCP Vertex AI

### Model Used

gemini-2.5-flash-preview-04-17

### Actual vs. Expected Behavior

Actual: `Max Tokens` slider is not shown for this model

Expected: Display `Max Tokens` slider, default to `65535` (maximum)

### Detailed Steps to Reproduce

N/A

### Relevant API Request Output

```shell
N/A
```

### Additional Context

N/A