Merge #14373: Consistency fixes for RPC descriptions

Summary:
b8edb9810a [rpc] Descriptions: Textual consistency fixes (Jon Layton)

Pull request description:

Tree-SHA512: fa22ddac94e95672579cc84309f1c3ea3a2dbf762e45a8ae9c121c4c5188bf8c19ff9458d49dd7ef760c3ae4226487612a2954e9a1a0e8b720116afeb718b46b

Backport of Core PR14373

Test Plan:

ninja
ninja check
./bitcoind
./bitcoin-cli help <changed rpcs>

Verify changes in help text.

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5517