Update dependency @types/jest to v26.0.15

Author: renovate-bot

package.json

@@ -34,7 +34,7 @@
     }
   },
   "devDependencies": {
-    "@types/jest": "26.0.14",
+    "@types/jest": "26.0.15",
     "jest": "26.6.0",
     "jest-fetch-mock": "3.0.3",
     "ts-jest": "26.4.1",