message: [Doc] importmulti: add missing description of keypool option
diff: @@ -1382,6 +1382,7 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
  {"internal", RPCArg::Type::BOOL, /* default */ "false", "Stating whether matching outputs should be treated as not incoming payments (also known as change)"},
  {"watchonly", RPCArg::Type::BOOL, /* default */ "false", "Stating whether matching outputs should be considered watchonly."},
  {"label", RPCArg::Type::STR, /* default */ "''", "Label to assign to the address, only allowed with internal=false"},
  + {"keypool", RPCArg::Type::BOOL, /* default */ "false", "Stating whether imported public keys should be added to the keypool for when users request new addresses. Only allowed when wallet private keys are disabled"},
  },
  },
  },
  