build: bump postcss from 8.4.45 to 8.4.47 in /code/frontend (#1321)

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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": "^1.40.0",
-        "postcss": "^8.4.45",
+        "postcss": "^8.4.47",
         "react": "^18.2.0",
         "react-dom": "^18.3.1",
         "react-markdown": "^9.0.1",