Update EMBER-DANDI Sandbox API URL

[NEStock]

Previously was https://api-dandi-sandbox.emberarchive.org/
Now is https://api-dandi.sandbox.emberarchive.org/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.85%. Comparing base (6f28a1c) to head (292527f).

❗ There is a different number of reports uploaded between BASE (6f28a1c) and HEAD (292527f). Click for more details.

HEAD has 346 uploads less than BASE

Flag	BASE (6f28a1c)	HEAD (292527f)
unittests	348	2

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1774       +/-   ##
===========================================
- Coverage   75.08%   52.85%   -22.24%     
===========================================
  Files          84       84               
  Lines       11910    11910               
===========================================
- Hits         8943     6295     -2648     
- Misses       2967     5615     +2648     

Flag	Coverage Δ
unittests	52.85% <ø> (-22.24%)	⬇️

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