Update dependency sinon to v7.2.6 (#427)

Author: renovate[bot]

package-lock.json

@@ -50,7 +50,7 @@
     "portfinder": "1.0.20",
     "selenium-assistant": "5.4.0",
     "semver": "5.6.0",
-    "sinon": "7.2.5",
+    "sinon": "7.2.6",
     "which": "1.3.1"
   },
   "engines": {