message: Remove unnecessary assert
  This assert ensures Last nTime is greater than First nTime
  however the code already accounts for this possiblity and
  therefore the assert is not needed.
diff: @@ -296,7 +296,6 @@ static arith_uint256 ComputeTarget(const CBlockIndex *pindexFirst,
  // In order to avoid difficulty cliffs, we bound the amplitude of the
  // adjustement we are going to do.
  - assert(pindexLast->nTime > pindexFirst->nTime);
  int64_t nActualTimespan = pindexLast->nTime - pindexFirst->nTime;
  if (nActualTimespan > 288 * params.nPowTargetSpacing)
  {
  