fix: remove pysilk_mod

requirements-optional.txt

@@ -16,7 +16,7 @@ dulwich
 # wechaty
 wechaty>=0.10.7
 wechaty_puppet>=0.4.23
-pysilk_mod>=1.6.0 # needed by send voice
+# pysilk_mod>=1.6.0 # needed by send voice only in wechaty
 
 # wechatmp wechatcom
 web.py