Update dependency portfinder to v1.0.25 (#517)

Author: renovate[bot]

package-lock.json

@@ -50,7 +50,7 @@
     "mkdirp": "0.5.1",
     "mocha": "6.2.1",
     "mocha-lcov-reporter": "1.3.0",
-    "portfinder": "1.0.24",
+    "portfinder": "1.0.25",
     "selenium-assistant": "5.4.0",
     "semver": "6.3.0",
     "sinon": "7.5.0",