See this edit for an example: a four years old question contains a link to the then-current documentation. The world has moved on since, and someone changes the old link to point to the new documentation instead. Is this appropriate? Would it be better to leave the old link alone (provided it's still valid) and add the link to the new version?
An edit should really only be approved if it materially improves the original post.
For this specific instance, and since MySQL 5.7 is still supported and available for download, the edit is unnecessary.
From the help:
Edits are expected to be substantial and to leave the post better than you found it. Common reasons for edits include:
- To fix grammar and spelling mistakes
- To clarify the meaning of the post (without changing that meaning)
- To include additional information only found in comments, so all of the information relevant to the post is contained in one place
- To correct minor mistakes or add updates as the post ages
- To add related resources or hyperlinks