Remove package opn (#4538)

For #4322

Author: DonJayamanne

package-lock.json

@@ -2185,7 +2185,6 @@
         "minimatch": "^3.0.4",
         "named-js-regexp": "^1.3.3",
         "node-stream-zip": "^1.6.0",
-        "opn": "^5.3.0",
         "pidusage": "^1.2.0",
         "reflect-metadata": "^0.1.12",
         "request": "^2.87.0",