Update dependency jest to v26

Author: renovate-bot

example/package.json

@@ -15,7 +15,7 @@
     "@ampproject/email-viewer": ".."
   },
   "devDependencies": {
-    "jest": "^25.2.0",
+    "jest": "^26.0.0",
     "jest-puppeteer": "^4.4.0",
     "puppeteer": "^2.1.1"
   },

package.json

@@ -41,7 +41,7 @@
     "@types/css-tree": "^1.0.3",
     "@types/jest": "^25.1.4",
     "gts": "^1.1.2",
-    "jest": "^25.2.0",
+    "jest": "^26.0.0",
     "jest-environment-jsdom-fourteen": "^1.0.1",
     "prettier": "^2.0.2",
     "rollup": "^2.2.0",