build: bump postcss from 8.4.38 to 8.4.39 in /code/frontend (#1103)

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

Author: dependabot[bot]

code/frontend/package-lock.json

@@ -19,7 +19,7 @@
         "lodash": "^4.17.21",
         "lodash-es": "^4.17.21",
         "microsoft-cognitiveservices-speech-sdk": "^1.38.0",
-        "postcss": "^8.4.38",
+        "postcss": "^8.4.39",
         "react": "^18.2.0",
         "react-dom": "^18.3.1",
         "react-markdown": "^9.0.1",