Bump react-syntax-highlighter from 15.5.0 to 15.6.1 in /app/frontend (Azure-Samples#2170)

Bumps [react-syntax-highlighter](https://github.com/react-syntax-highlighter/react-syntax-highlighter) from 15.5.0 to 15.6.1.
- [Release notes](https://github.com/react-syntax-highlighter/react-syntax-highlighter/releases)
- [Changelog](https://github.com/react-syntax-highlighter/react-syntax-highlighter/blob/master/CHANGELOG.MD)
- [Commits](react-syntax-highlighter/react-syntax-highlighter@15.5.0...v15.6.1)

---
updated-dependencies:
- dependency-name: react-syntax-highlighter
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

app/frontend/package-lock.json

@@ -30,7 +30,7 @@
     "react-router-dom": "^6.26.2",
     "react-helmet-async": "^2.0.5",
     "react-i18next": "^15.1.1",
-    "react-syntax-highlighter": "^15.5.0",
+    "react-syntax-highlighter": "^15.6.1",
     "rehype-raw": "^7.0.0",
     "remark-gfm": "^4.0.0",
     "scheduler": "^0.20.2"