feat: remove Transifex calls for OEP-58 for discussion MFE

[sundasnoreen12]

INF-1279
Similar to 887

Description

Changes

1. Removes all direct use of tx pull and tx push commands from the micro-frontend in favor of the atlas pull command.
2. Remove source and language translations from the repositories, hence no .json files will be committed into the repos.
3. src/i18n/index.js should export and empty array so the make pull_translations override it with the dynamic list of languages.
4. Remove the experimental OPENEDX_ATLAS_PULL flag to make atlas pull the default.
5. Remove all Transifex related Makefile targets and other files.

Merge Checklist

• If your update includes visual changes, have they been reviewed by a designer? Send them a link to the Sandbox, if applicable.
• Is there adequate test coverage for your changes?

Post-merge Checklist

• Deploy the changes to prod after verifying on stage or ask @openedx/edx-infinity to do it.
• 🎉 🙌 Celebrate! Thanks for your contribution.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.82%. Comparing base (1a2068d) to head (cb6d336).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #682   +/-   ##
=======================================
  Coverage   92.82%   92.82%           
=======================================
  Files         158      158           
  Lines        3331     3331           
  Branches      919      919           
=======================================
  Hits         3092     3092           
  Misses        219      219           
  Partials       20       20           

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