Regenerating params in VS code when the bicepparam file exists produces a confusing error message

[majastrz]

Bicep version
0.32.4

Describe the bug
Regenerating params in VS code when the bicepparam file exists produces the following error message:

8:17:19 PM: Generating parameters file failed. The file "main.bicepparam" already exists but does not contain the schema for a parameters file. If overwriting the file is intended, delete it manually and retry the Generate Parameters command.

To Reproduce

1. Create an empty bicep file and save it
2. Right click on the editor tab and then click "Generate Parameters File"
3. Choose bicepparam and all (the 2nd choice doesn't matter)
4. Param generation should succeed.
5. Repeat 2 and 3
6. Now you should get the message above

Additional context
A valid bicepparam file will never contain the JSON param schema anywhere. We should not be checking for that. I suspect we're reusing the JSON param logic incorrectly.