docs: fix initial data doc

[fyliu]

Problem discovered in this issue

• 303

Overview

We need to fix the create initial data scripts page. The guide has a bug in the code which makes code created with the guide non-functional. The data migration files aren't reversible, so we should fix that.

Action Items

• [x] fix the guide

Resources/Instructions

Here's the page that contains the error.

• the last line in the migration script should have 4 more spaces of indentation

[fyliu]

I already did made the fix but needed an issue for the PR. The first one is the problem but I found a few more things and fixed them as well.