DOC: add newline to fix code block format in `pandas.DataFrame.to_sql`
- [x] closes #36922 
- [x] tests added / passed n/a (didn't add any new tests/change code)
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

not sure if i need to add a whatsnew entry to 1.1.4 or 1.2.0...

would love to get a hacktoberfest tag if your org supports this. #36837 