[BUG] Removing preview version from typespec causes TSV Validation error

### API Spec link

https://github.com/Azure/azure-rest-api-specs/tree/main/specification/widget/resource-manager/Microsoft.Widget/Widget

### API Spec version

2012-10-01-preview

### Describe the bug

Example of failure here: https://github.com/Azure/azure-rest-api-specs/pull/40169

In both fsv1 and fsv2, the check to allow old previews to be deleted fails unless the x-typespec-generated comment is removed.

Need to update the check to allow remving a preview version ins TypeSpec but retain the swagger as is.

### Expected behavior

TSV should succeed for both specs in the pr

### Actual behavior

TSV fails for both specs with:

Rule Compile failed

Output folder '.' appears to contain TypeSpec-generated swagger files, not generated from the current TypeSpec sources. Perhaps you deleted a version from your TypeSpec, but didn't delete the associated swaggers?

preview\2021-10-01-preview\widget.json

### Reproduction Steps

https://github.com/Azure/azure-rest-api-specs/pull/40169

### Environment

Hosting platform is irrelevant for this issue