Hopefully fix ZSM playback by removing obsolete code I forgot about

backends/playback/zsm/zsm_backend.cpp

@@ -265,9 +265,6 @@ void ZsmBackend::tick(bool step) {
             } break;
         }
     }
-    while (ym_pairs.size() > 0) {
-        reg_pair pair = ym_pairs.pop();
-    }
     size_t nextCpuClocksInt = std::floor(nextCpuClocks);
     size_t prevCpuClocksInt = std::floor(prevCpuClocks);
     size_t cpuClocksIntDelta = nextCpuClocksInt - prevCpuClocksInt;