Here's my answer if the edit were really by a newbie with low rep: let it stand if it's correct.
When I see newbie answers to old already answered questions I'll sometimes comment with a welcome message, then mildly suggests that this particular contribution didn't add much, but that I hoped to see more posts that did. I don't downvote.
I remember that when I was new I wanted to exercise my chance to make everything better here. The fact that I could make (minor) edits made me feel welcome in the community. After a while I realized those small fixes were unnecessary, and even distracting if they bumped old posts to the front page.
I still fix many typos in question titles - perhaps more than I should.
Edit: Here's a recent example. not from a new user (shortly after I posted my answer):