Bump uglify-js from 3.9.1 to 3.9.2 (josdejong#980)

Bumps [uglify-js](https://github.com/mishoo/UglifyJS2) from 3.9.1 to 3.9.2.
- [Release notes](https://github.com/mishoo/UglifyJS2/releases)
- [Commits](mishoo/UglifyJS@v3.9.1...v3.9.2)

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package.json

@@ -53,7 +53,7 @@
     "mocha": "7.1.2",
     "source-map-loader": "0.2.4",
     "standard": "14.3.3",
-    "uglify-js": "3.9.1",
+    "uglify-js": "3.9.2",
     "webpack": "4.43.0"
   },
   "files": [