DOC: code example isn't formatted in `pandas.DataFrame.to_sql`
#### Location of the documentation

The code example in [pandas.DataFrame.to_sql](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.to_sql.html?highlight=to_sql#pandas.DataFrame.to_sql) isn't formatted properly.

(it's the example that inserts User 4 and User 5 into the db)

**Note**: You can check the latest versions of the docs on `master` [here](https://pandas.pydata.org/docs/dev/).

#### Documentation problem

![image](https://user-images.githubusercontent.com/29909203/95242497-1d361480-07c4-11eb-9dd5-fa1eea90413f.png)

oh no, the code isn't formatted correctly!

#### Suggested fix for documentation

The reason is there's no blank line before the code snippet, see:

https://github.com/pandas-dev/pandas/blob/b58ee5779583b31de513b3d5c12f5c69c035e920/pandas/core/generic.py#L2692-L2695

Add a blank line above the code snippet :), i have a PR in progress