Some image files store in firebase storage don't have the correct content

### Describe the Bug

_A clear and concise description of the bug._
Some images (such as person pictures or seat pictures) stored in firebase storage don't have the same content as their sources.

My guess is that cdp-backend tries to download the image content from one of the [URIs](https://github.com/CouncilDataProject/cdp-scrapers/blob/main/cdp_scrapers/instances/seattle-static.json#L41) in the JSON file and when it fails the failed content was uploaded to firebase storage instead of the image content.

I think the solution here is to make sure the step to download the image is successful?

### Expected Behavior

_What did you expect to happen instead?_
Image content stored in firebase storage should be the same as the original images.

### Reproduction

_Steps to reproduce the behavior and/or a minimal example that exhibits the behavior._

This is the actual content of the above firebase storage URI (it doesn't look like it could be an image file):

### Environment

_Any additional information about your environment._

- OS Version: _[e.g. macOS 11.3.1]_
- CDP Backend Version: _[e.g. 0.5.0]_

cc @JacksonMaxfield @dphoria