Fix error message formatting in delete method (#676)

## Description

Currently, the error here looks like this:
<img width="558" height="124" alt="image"
src="https://github.com/user-attachments/assets/64df8652-30f2-46eb-9abe-430406a4a6a4"
/>


### Introduces a breaking change?

- [ ] Yes
- [x] No

### Type of change

- [ ] Bug fix (change which fixes an issue)
- [ ] New feature (change which adds functionality)
- [ ] Documentation update (improves or adds clarity to existing
documentation)
- [x] Other (chores, tests, code style improvements etc.)

### Tested on

- [x] iOS
- [x] Android

### Testing instructions

<!-- Provide step-by-step instructions on how to test your changes.
Include setup details if necessary. -->

### Screenshots

<!-- Add screenshots here, if applicable -->

### Related issues

<!-- Link related issues here using #issue-number -->

### Checklist

- [ ] I have performed a self-review of my code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have updated the documentation accordingly
- [x] My changes generate no new warnings

### Additional notes

<!-- Include any additional information, assumptions, or context that
reviewers might need to understand this PR. -->

Author: msluszniak

packages/react-native-executorch/src/controllers/OCRController.ts

@@ -96,7 +96,7 @@ export class OCRController {
     if (this.isGenerating) {
       throw new Error(
         getError(ETError.ModelGenerating) +
-          'You cannot delete the model. You must wait until the generating is finished.'
+          ', You cannot delete the model. You must wait until the generating is finished.'
       );
     }
     this.nativeModule.unload();