Merge #12584: Fix typos and cleanup documentation

Summary:
a9761cae1c Fix typos and cleanup (Dimitris Apostolou)

Pull request description:

[ci-skip]

Tree-SHA512: 6d7e02d8fdf6add702bbfe4439ace9c8621b45d21111abc69d85be9120347b06a029bc1885665547c1230ebc41da9d97210f6d1325b7692a4585356969ecb127

Backport of Core PR12584
https://github.com/bitcoin/bitcoin/pull/12584/files

Test Plan: Read it.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D3204