Fix github url strings (org edx -> openedx)

[sarina]

This PR was autogenerated

This pr replaces the old GitHub organization, github.com/edx, with the new GitHub organization, github.com/openedx.

Tagging @openedx/tcril-engineering for review, but others are welcome to provide review.

Ref: openedx/axim-engineering#42

[codecov]

Codecov Report

Base: 93.43% // Head: 93.43% // No change to project coverage 👍

Coverage data is based on head (9b8d841) compared to base (4367be5).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #177   +/-   ##
=======================================
  Coverage   93.43%   93.43%           
=======================================
  Files          18       18           
  Lines        1996     1996           
  Branches      183      183           
=======================================
  Hits         1865     1865           
  Misses        118      118           
  Partials       13       13           

Flag	Coverage Δ
unittests	93.43% <ø> (ø)

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