Update dependency mocha to v6.2.2 (#518)

Author: renovate[bot]

package-lock.json

@@ -48,7 +48,7 @@
     "geckodriver": "1.19.0",
     "istanbul": "0.4.5",
     "mkdirp": "0.5.1",
-    "mocha": "6.2.1",
+    "mocha": "6.2.2",
     "mocha-lcov-reporter": "1.3.0",
     "portfinder": "1.0.25",
     "selenium-assistant": "5.4.0",