`NopFilter` is still marked with `TPEXP`

## Describe the bug

The `NopFilter` class, which has been in MTP since 1.0.2 and is presumably stable, is still marked with `TPEXP`. It should not be.

## Steps To Reproduce

* Use `NopFilter`
* Get `TPEXP` compiler warning

## Expected behavior

Should be usable without `#pragma warning disable TPEXP`.

## Actual behavior

Can't. 😄 
