Fix readme heading level

readme.md

@@ -208,7 +208,7 @@ In production on your own site, you'll need to change this to:
 
 and configure [SMTP settings](https://docs.djangoproject.com/en/3.2/topics/email/#smtp-backend) appropriate for your email provider.
 
-## Testing Content-Security-Policy compliance in Wagtail
+### Testing Content-Security-Policy compliance in Wagtail
 
 Bakerydemo is set up in such a way that it can be used to test [Content-Security-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP) compatibility in Wagtail. It uses [django-csp](https://django-csp.readthedocs.io/en/latest/index.html) to generate the appropriate [CSP HTTP header](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy).