voice.go: remove runtime.LockOSThread call from opusSender (#404)

runtime.LockOSThread does not do anything for performance and is instead
intended for interfacing with libraries that use thread local data structures.

Closes #402

voice.go

@@ -15,7 +15,6 @@ import (
 	"fmt"
 	"log"
 	"net"
-	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -659,8 +658,6 @@ func (v *VoiceConnection) opusSender(udpConn *net.UDPConn, close <-chan struct{}
 		return
 	}
 
-	runtime.LockOSThread()
-
 	// VoiceConnection is now ready to receive audio packets
 	// TODO: this needs reviewed as I think there must be a better way.
 	v.Lock()