Silero Models EN V2 Released

Almost forgot to announce it!

- New EN V2 model - https://github.com/snakers4/silero-models/issues/20#issuecomment-720932378
- Quality benchmarks - https://github.com/snakers4/silero-models/wiki/Quality-Benchmarks#en-v2

A minor release, i.e. other models not affected.

English model was made much more robust to certain dialects. The model should generalize much better in general.