关于 lalb 文档里面 base_weight 的理解

**Describe the bug (描述bug)**
怎么理解lalb文档里面关于base_weight的下面这句话的描述？

'除了待删除节点，所有节点的权值绝对不会为0。'

https://github.com/apache/brpc/blob/master/docs/cn/lalb.md
因为根据 https://github.com/apache/brpc/issues/820 ， base_weight是有可能为0值的

**To Reproduce (复现方法)**

**Expected behavior (期望行为)**

**Versions (各种版本)**
OS:
Compiler:
brpc:
protobuf:

**Additional context/screenshots (更多上下文/截图)**

Read docs/cn/lalb.md and compare the statement about base_weight with the behavior described in issue #820. Determine whether the documentation is inaccurate or needs clarification, then update the relevant wording so it accurately explains when a node's weight can be zero.

Written by the indexing model from the issue text.