Bump vega-expression from 5.2.0 to 5.2.1 in /packages/powerbi (#778)

Bumps [vega-expression](https://github.com/vega/vega) from 5.2.0 to 5.2.1.
- [Release notes](https://github.com/vega/vega/releases)
- [Commits](https://github.com/vega/vega/commits)

---
updated-dependencies:
- dependency-name: vega-expression
  dependency-version: 5.2.1
  dependency-type: indirect
...

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Author: dependabot[bot]