fix: upgrade pm2 from 5.2.0 to 5.3.1

Snyk has created this PR to upgrade pm2 from 5.2.0 to 5.3.1.

See this package in npm:
https://www.npmjs.com/package/pm2

See this project in Snyk:
https://app.snyk.io/org/blinkhash/project/5109047e-f8d9-4e22-915d-ade5d907f6c1?utm_source=github&utm_medium=referral&page=upgrade-pr

package.json

@@ -57,7 +57,7 @@
     "express-rate-limit": "^5.5.1",
     "foundation-stratum": "0.0.42",
     "nodemon": "2.0.15",
-    "pm2": "^5.2.0",
+    "pm2": "^5.3.1",
     "redis": "^3.1.1"
   },
   "devDependencies": {