Update edit link in 2.x docs

[discdiver]

First check

• [X] I added a descriptive title to this issue.
• [X] I used GitHub search to find a similar request and didn't find it 😇

Describe the issue

The edit link in 2.x is going to the main prefecthq/prefect branch, which builds the 3.x docs.

Describe the proposed change

If we can change the branch, I will. If not, I’ll remove the pencil.

Additional context

Thank you, Thomas.

[discdiver]

completed