[LTP] [PATCH 3/3] doc: Fix typo in max_runtime docs

[Yang Xu (Fujitsu)]

Hi Petr, Martin

> Hi Martin,
> 
> I merged this simple fix.
> And I'll ask in "LTP release preparations" thread for merging this.

This patchset is LGTM, I don't see this email and has merged this 
patchset, sorry.

ps: This patchset is simple change, so I guess it will not affect
a lot for "LTP release preparations".

Best Regards
Yang Xu
> Thanks!
> 
> Kind regards,
> Petr
>