One thing that an AI could do better than humans is to actually stay on top of software changes over time. The number of cases where I have been following official documentation, only to find out that the current version doesn't actually work that way is absurd--and it would still be absurd even if it was only 1 (it's not).

Assuming the AI is able to access and understand the source code, it could at least make sure the current methods or variables or whatever match what the code does at any given time. We'd still need humans for other parts of technical documentation, at least for awhile yet, but this part is something that is already much better handled by a computer.