Update dependency jest to v26

Author: renovate-bot

package.json

@@ -24,7 +24,7 @@
     "request": "2.88.0"
   },
   "devDependencies": {
-    "jest": "24.7.1",
+    "jest": "26.4.2",
     "nock": "10.0.6",
     "nodemon": "1.19.1",
     "smee-client": "1.1.0",