[fix] add field comments and delete useless fields.

[ramsayleung]

Description

htsec 卖出和买入模板的有三个字段BaseUnit, TargetUnit, CommissionUnit是被定义与赋值了，但是未在模板中使用的，猜测是拷贝自 huobi 模板，因此希望将无用字段删除，降低维护和心智成本.

Modification

概括:

1. ledger -htsec模板增加字段说明
2. htsec模板 删除无用字段

Motivation and Context

97

Dependencies

None

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How has this been tested?

make test: all tests pass