Partners: Image field character length should be extended on DB

[manjitapandey]

Describe the bug
I am unable to upload image link on partners page. Shows 500 error on network panel

To Reproduce
Make sure you have admin access to the platform
Steps to reproduce the behavior:

1. Go to 'Manage'
2. Click on 'partners'
3. Click on 'new
4. upload image link
5. See error

Expected behavior
The image should be uploaded and should be visible on partners statistics page

Additional context
The word "image" doesn't provide proper meaning since users will be uploading link of their logo. The terms "Partner's logo" would fit more.
cc: @ramyaragupathy , @royallsilwallz , @prabinoid