Bump @azure/msal-react from 2.0.6 to 2.0.21 in /app/frontend (#1849)

Bumps [@azure/msal-react](https://github.com/AzureAD/microsoft-authentication-library-for-js) from 2.0.6 to 2.0.21.
- [Release notes](https://github.com/AzureAD/microsoft-authentication-library-for-js/releases)
- [Commits](AzureAD/microsoft-authentication-library-for-js@msal-react-v2.0.6...msal-react-v2.0.21)

---
updated-dependencies:
- dependency-name: "@azure/msal-react"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Pamela Fox <[email protected]>