os: createHardlink: clarify documentation
os: createHardlink: clarify documentation

I know no (UNIX-like) system which restricts creation of hardlinks.

dom96/Nim,jfhg/Nim,haiodo/Nim,singularperturbation/Nim,singularperturbation/Nim,dom96/Nim,jfhg/Nim,jfhg/Nim,russpowers/Nim,russpowers/Nim,russpowers/Nim,jfhg/Nim,jfhg/Nim,russpowers/Nim,haiodo/Nim,dom96/Nim,jfhg/Nim,haiodo/Nim,haiodo/Nim,jfhg/Nim,dom96/Nim,russpowers/Nim,dom96/Nim,haiodo/Nim,tulayang/Nim,russpowers/Nim,singularperturbation/Nim,tulayang/Nim,haiodo/Nim,singularperturbation/Nim,tulayang/Nim,singularperturbation/Nim,dom96/Nim,singularperturbation/Nim,tulayang/Nim,russpowers/Nim,singularperturbation/Nim,tulayang/Nim,tulayang/Nim,haiodo/Nim,dom96/Nim