message: Fix computation for smoothed runtime TPS statistic
  Was incorrectly removing the instantaneous rate instead of the smoothed rate.
  This did not cause an issue until a full 24-hours worth of samples were taken.
diff: @@ -281,7 +281,7 @@ void TransactionGraphWidget::setTransactionsPerSecond(double nTxPerSec,
  // Purge smoothed sample(s) that have moved beyond the sample set size limit
  while (vSmoothedSamples.size() > MAXIMUM_SAMPLES_TO_KEEP)
  {
  - float fRemoving = vInstantaneousSamples.last();
  + float fRemoving = vSmoothedSamples.last();
  // Adjust smoothed mean for total sample set to exclude the sample being purged
  fSmoothedTpsAverage_Sampled =
  SubtractFromArithmeticMean(fSmoothedTpsAverage_Sampled, vSmoothedSamples.size(), fRemoving);
  