default VAD to "ovos-vad-plugin-webrtcvad" + setup/requirements cleanup

[JarbasAl]

No description provided.

[codecov]

Codecov Report

Merging #271 (ea4e506) into dev (6ceb058) will increase coverage by 2.23%.
The diff coverage is 43.37%.

@@            Coverage Diff             @@
##              dev     #271      +/-   ##
==========================================
+ Coverage   50.35%   52.59%   +2.23%     
==========================================
  Files         119      156      +37     
  Lines       10077     8165    -1912     
==========================================
- Hits         5074     4294     -780     
+ Misses       5003     3871    -1132     

Impacted Files	Coverage Δ
mycroft/audio/__main__.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/__main__.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/mark1/arduino.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/mark1/eyes.py	0.00% <0.00%> (ø)
mycroft/client/enclosure/mark1/mouth.py	0.00% <0.00%> (ø)
mycroft/client/speech/__main__.py	0.00% <0.00%> (ø)
mycroft/client/speech/hotword_factory.py	0.00% <0.00%> (-88.89%)	⬇️
mycroft/client/speech/service.py	0.00% <0.00%> (ø)
mycroft/client/speech/silence.py	0.00% <0.00%> (-42.86%)	⬇️
mycroft/client/text/__init__.py	0.00% <0.00%> (ø)
... and 154 more

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