[backport#14103] docs: Fix broken Doxygen comments

Summary:
Fix incorrect Doxygen comments (practicalswift)

Pull request description:

Fix broken Doxygen comments.

This commit was taken from #13914 which now only covers `-Wdocumentation`.

https://github.com/bitcoin/bitcoin/pull/14103/commits/0e534d4dcae91ecf7ebd7a667227f7c26b4d5755

Backport of Core PR14103

Test Plan:

read them

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7059