ruby : Add no_speech_thold (#2641)

ruby : Add no_speech_thold (#2641)

* Remove Whisper::Model.[]

* Fix Whisper::Model::URI#request

* Make Whisper::Context#initialize accept pre-converted model name

* Use downloading pre-converted model feature for testing

* Update README

* Remove unnecessary task

* Move whisper/model.rb -> whisper/model/uri.rb

* Update document comment of Whisper::Context#initialize

* Don't show download progress when not tty

* Pass String to raise

* Use cache model file if download fails

* Add test for auto download

* Specify required Ruby version

* Fix a typo

* Remove unnecessary flags

* Initialize Whisper::Params#diarize explicitely

* Remove redundant code from README for simplicity

* Add Whisper::Params#no_speech_thold attribute

* Add test for Whisper::Params#no_speech_thold