Port #4182 from Citra: "Prefix all size_t with std::"

src/audio_core/time_stretch.cpp

@@ -26,7 +26,8 @@ void TimeStretcher::Flush() {
     m_sound_touch.flush();
 }
 
-size_t TimeStretcher::Process(const s16* in, size_t num_in, s16* out, size_t num_out) {
+std::size_t TimeStretcher::Process(const s16* in, std::size_t num_in, s16* out,
+                                   std::size_t num_out) {
     const double time_delta = static_cast<double>(num_out) / m_sample_rate; // seconds
 
     // We were given actual_samples number of samples, and num_samples were requested from us.