Bump pdfjs-dist from 2.3.200 to 2.4.456 (#1518)

Bumps [pdfjs-dist](https://github.com/mozilla/pdfjs-dist) from 2.3.200 to 2.4.456.
- [Release notes](https://github.com/mozilla/pdfjs-dist/releases)
- [Commits](https://github.com/mozilla/pdfjs-dist/compare/v2.3.200...v2.4.456)

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package.json

@@ -60,7 +60,7 @@
     "minimatch-browser": "^1.0.0",
     "moment": "^2.27.0",
     "moment-es6": "1.0.0",
-    "pdfjs-dist": "2.3.200",
+    "pdfjs-dist": "2.4.456",
     "rxjs": "^6.6.0",
     "tslib": "^2.0.0",
     "zone.js": "~0.10.2"