message: [RPC] fix help texts
  getblockindexstats
  getmintsinblocks
  getserials
diff: @@ -1301,7 +1301,7 @@ void validaterange(const UniValue& params, int& heightStart, int& heightEnd, int
  UniValue getmintsinblocks(const UniValue& params, bool fHelp) {
  if (fHelp || params.size() != 3)
  throw runtime_error(
  - "getmintsinblocks <height> <range> [coinDenomination]\n"
  + "getmintsinblocks height range coinDenomination\n"
  "\nReturns the number of mints of a certain denomination"
  "\noccurred in blocks [height, height+1, height+2, ..., height+range-1]\n"
  @@ -1354,7 +1354,7 @@ UniValue getmintsinblocks(const UniValue& params, bool fHelp) {
  UniValue getserials(const UniValue& params, bool fHelp) {
  if (fHelp || params.size() < 2 || params.size() > 3)
  throw runtime_error(
  - "getserials <height> <range> [fVerbose]\n"
  + "getserials height range ( fVerbose )\n"
  "\nLook the inputs of any tx in a range of blocks and returns the serial numbers for any coinspend.\n"
  "\nArguments:\n"
  @@ -1461,7 +1461,7 @@ UniValue getserials(const UniValue& params, bool fHelp) {
  UniValue getblockindexstats(const UniValue& params, bool fHelp) {
  if (fHelp || params.size() < 2 || params.size() > 3)
  throw runtime_error(
  - "getblockindexstats <height> <range> [fFeeOnly]\n"
  + "getblockindexstats height range ( fFeeOnly )\n"
  "\nReturns aggregated BlockIndex data for blocks "
  "\n[height, height+1, height+2, ..., height+range-1]\n"
  