refactor(sointu): change the name of AudioSink into AudioOutput

The interface is never used as anything else as Output so trying to generalize as something more vague like Sink made no sense.

oto/oto.go

@@ -13,7 +13,7 @@ type OtoOutput struct {
 	tmpBuffer []byte
 }
 
-func (c *OtoContext) Output() sointu.AudioSink {
+func (c *OtoContext) Output() sointu.AudioOutput {
 	return &OtoOutput{player: (*oto.Context)(c).NewPlayer(), tmpBuffer: make([]byte, 0)}
 }