Export-RegEx -As EmbeddedEngine is a no-op

**Describe the bug**

Export-RegEx -As EmbeddedEngine does nothing

**To Reproduce**

```PowerShell
Export-RegEx -As EmbeddedEngine -Name * -Path .\Test.ps1
```

Does not create test.ps1, or error out.


**Additional context**


It appears that this has been internally renamed to 'Embedded', but not updated in the [ValidateSet()] of Get-RegEx or Export-RegEx.
