change dropbox links

[meganrm]

Problem

Dropbox links to OBJ files started having a CORS error

Solution

I replaced the www.dropbox.com with dl.dropboxusercontent.com
based on this post
They do note in the post that dl.dropboxusercontent.com is an old style that they still support "for now" so we'll have to keep an eye on it. I did ask in the forum if they plan to address the CORS issue with the new link style, so we'll see what they say.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• This change requires updated or new tests

Steps to Verify:

1. npm start
2. open test bed viewer
3. drag and drop this file
4. should see structures

Screenshots (optional):

[github-actions]

jest coverage report 🧪

Total coverage

Status	Category	Percentage	Covered / Total
🔴	Statements	40.18%	1962/4882
🔴	Branches	43.88%	821/1871
🔴	Functions	37.13%	404/1088
🔴	Lines	40.46%	1880/4646

Status of coverage: 🟢 - ok, 🟡 - slightly more than threshold, 🔴 - under the threshold