Closes ENG-1035

Description Of Changes

A prior PR added this env parameter into the Docker build, but the way the fides-js build script works, it's specifying a specific set of env parameters. So we need to explicitly pass it, rather than relying on process.env.

Code Changes

• Update fides-js npm build script to parse and pass the IS_TEST env variable

Steps to Confirm

1. Get the privacy center up and running
2. Run npm run build on fides-js to see the testids removed.
3. Set the IS_TEST env variable in the console by running export IS_TEST=true
4. Run npm run build again; the testids should now be present. (For example, in the Manage Preferences button).

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Add a db-migration This indicates that a change includes a database migration label to the entry if your change includes a DB migration
  • Add a high-risk This issue suggests changes that have a high-probability of breaking existing code label to the entry if your change includes a high-risk change (i.e. potential for performance impact or unexpected regression) that should be flagged
  • Updates unreleased work already in Changelog, no new entry necessary
• Followup issues:
  • Followup issues created
  • No followup issues
• Database migrations:
  • Ensure that your downrev is up to date with the latest revision on main
  • Ensure that your downgrade() migration is correct and works
    • If a downgrade migration is not possible for this change, please call this out in the PR description!
  • No migrations
• Documentation:
  • Documentation complete, PR opened in fidesdocs
  • Documentation issue created in fidesdocs
  • If there are any new client scopes created as part of the pull request, remember to update public-facing documentation that references our scope registry
  • No documentation updates required