Update dependency ts-jest to v26.4.0

Author: renovate-bot

package-lock.json

@@ -44,7 +44,7 @@
     "prettier": "2.1.2",
     "subscriptions-transport-ws": "0.9.18",
     "supertest": "4.0.2",
-    "ts-jest": "26.3.0",
+    "ts-jest": "26.4.0",
     "ts-node": "9.0.0",
     "ts-node-dev": "1.0.0-pre.62",
     "typescript": "4.0.3"