build: remove unused @edx/reactifex package (#595)

* build: remove unused @edx/reactifex package

Remove @edx/reactifex package from devDependencies as it is no longer
needed. Translation extraction functionality has been verified to work
correctly without this dependency.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

* chore: package-lock.json

Updating package-lock

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Co-authored-by: Claude <[email protected]>
Co-authored-by: Deborah Kaplan <[email protected]>

Author: 3 people