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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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