Substantial edits that change the intent or meaning of a post should be avoided.

In this case, I would write a new answer, explain it is from this year and the top answer is old, something like

The answers here are a bit old, this one is an up to date solution.

then, given their is only one other good answer on that question, people should see it and voting should sort it out with time.

I strongly advise against adding anything about a new answer to the old answer, it will come off as vandalism and begging for votes on the new answer and may annoy the OP or other users.

Substantial edits that change the intent or meaning of a post should be avoided.

In this case, I would write a new answer, explain it is from this year and the top answer is old, something like

The answers here are a bit old, this one is an up to date solution.

then, given their is only one other good answer on that question, people should see it and voting should sort it out with time.

I strongly advise against adding anything about a new answer, without permission from the OP, to the old answer, it will come off as vandalism and begging for votes on the new answer and may annoy the OP or other users.