Removes path manipulation workaround. Please see https://github.com/yarnpkg/yarn/issues/5874

[akolson]

Summary

This pr removes manipulation of $PATH, a workaround used in previous versions of yarn. This seems to have been fixed as indicated in yarnpkg/yarn#5874

References

NA

Reviewer guidance

Set up the development environment as specified in https://kolibri-dev.readthedocs.io/en/develop/getting_started.html should result in successfully running kolibri locally without returning build errors

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[rtibbles]

Changes look correct, local testing checks out.