sink: Change EnqueueSamples to take a pointer to a buffer instead of a std::vector

src/audio_core/null_sink.h

@@ -19,7 +19,7 @@ public:
         return native_sample_rate;
     }
 
-    void EnqueueSamples(const std::vector<s16>&) override {}
+    void EnqueueSamples(const s16*, size_t) override {}
 
     size_t SamplesInQueue() const override {
         return 0;