chore(package): update @types/ioredis to version 4.0.20

Author: greenkeeper[bot]

package.json

@@ -47,7 +47,7 @@
   },
   "devDependencies": {
     "@types/chai": "^4.1.6",
-    "@types/ioredis": "4.0.19",
+    "@types/ioredis": "4.0.20",
     "@types/chai-as-promised": "7.1.1",
     "@types/mocha": "^5.2.5",
     "@types/node": "12.12.9",