Merge #11155: Trivial: Documentation fixes for CVectorWriter ctors

Summary:
37c4362f2 Trivial: Documentation fixes for CVectorWriter ctors (danra)

Pull request description:

Tree-SHA512: 13aef27f6b38dc276db6616d13e243a5413acf3a3ece5a52578c07b97a5bc9da337e7e230fcdb91727ec88b199844fd9aa3a88e7d96c911c119c91070a892ba1

Backport of Core PR11155
https://github.com/bitcoin/bitcoin/pull/11155/

Test Plan: make check

Reviewers: jasonbcox, Fabien, deadalnix, O1 Bitcoin ABC, #bitcoin_abc, markblundeberg

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, markblundeberg

Differential Revision: https://reviews.bitcoinabc.org/D2982