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: 62.58% // Head: 62.58% // No change to project coverage 👍

Coverage data is based on head (ba209fd) compared to base (bf64a82).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #257   +/-   ##
=======================================
  Coverage   62.58%   62.58%           
=======================================
  Files          15       15           
  Lines         278      278           
  Branches       66       66           
=======================================
  Hits          174      174           
  Misses        103      103           
  Partials        1        1           

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