[PATCH v2] manual: Correct return value description of 'clock_nanosleep'

[Maciej W. Rozycki]

On Mon, 2 Jun 2025, Arjun Shankar wrote:

> Seems reasonable to me. Would you like to post a patch to this effect?
> Or would you like me to do it? I can later this week once I finish
> another manual change I'm trying to get done.

 I have now posted an update with a minor wording adjustment to match our 
predominant style and a fix too for a format tag issue I discovered in the 
course.

  Maciej