fix: upgrade ioredis from 4.14.1 to 4.15.1

Snyk has created this PR to upgrade ioredis from 4.14.1 to 4.15.1.

See this package in NPM:
https://www.npmjs.com/package/ioredis

See this project in Snyk:
https://app.snyk.io/org/bluewallet/project/29c066bc-abce-44d9-b68e-064466e610e7?utm_source=github&utm_medium=upgrade-pr

package.json

@@ -27,7 +27,7 @@
     "express": "^4.16.4",
     "express-rate-limit": "^3.4.0",
     "grpc": "^1.17.0-pre1",
-    "ioredis": "^4.2.0",
+    "ioredis": "^4.15.1",
     "jayson": "^2.1.0",
     "morgan": "^1.9.1",
     "mustache": "^3.0.1",