Sponsorship application does not accept svg files for Sponsor print logo

[loren-c]

Describe the bug
When a sponsor uploads an SVG file to the field "Sponsor print logo" when submitting sponsorship information at https://www.python.org/sponsors/application/new/ and hit Apply it returns "*Upload a valid image. The file you uploaded was either not an image or a corrupted image."

To Reproduce
Steps to reproduce the behavior:

1. Go to https://www.python.org/psf/sponsorship/
2. Select a packed and hit "Submit"
3. Scroll down to "Sponsor print logo" (If your account is already associated with a sponsor, you will need to select "create a new one" to show this field)
4. See error

Expected behavior
SVG file uploads succesfully

Screenshots

Desktop (please complete the following information):

• OS: mac
• Browser firefox

@ewdurbin