[misc] install bunyan as production dependency

```
Error: Cannot find module 'bunyan'
Require stack:
- .../node_modules/@google-cloud/logging-bunyan/build/src/middleware/express.js
- .../node_modules/@google-cloud/logging-bunyan/build/src/index.js
- .../node_modules/logger-sharelatex/logging-manager.js
- .../node_modules/logger-sharelatex/index.js
- .../app.js
```

services/track-changes/package-lock.json

@@ -1638,14 +1638,12 @@
       "integrity": "sha512-lGzLKcioL90C7wMczpkY0n/oART3MbBa8R9OFGE1rJxoVI86u4WAGfEk8Wjv10eKSyTHVGkSo3bvBylCEtk7LA=="
     },
     "bunyan": {
-      "version": "2.0.2",
-      "resolved": "https://registry.npmjs.org/bunyan/-/bunyan-2.0.2.tgz",
-      "integrity": "sha512-9/tdl5YpJ2FR1ldac8y+hAC3rLaVzXnrd1ZATS+ehg5VCpD+5vltW9VVWbMF8o5qiw4uQO0nEFK/wL7B2SDvpg==",
-      "dev": true,
+      "version": "1.8.15",
+      "resolved": "https://registry.npmjs.org/bunyan/-/bunyan-1.8.15.tgz",
+      "integrity": "sha512-0tECWShh6wUysgucJcBAoYegf3JJoZWibxdqhTm7OHPeT42qdjkZ29QCMcKwbgU1kiH+auSIasNRXMLWXafXig==",
       "requires": {
         "dtrace-provider": "~0.8",
-        "exeunt": "1.1.0",
-        "moment": "^2.10.6",
+        "moment": "^2.19.3",
         "mv": "~2",
         "safe-json-stringify": "~1"
       }
@@ -2837,12 +2835,6 @@
       "resolved": "https://registry.npmjs.org/events/-/events-1.1.1.tgz",
       "integrity": "sha512-kEcvvCBByWXGnZy6JUlgAp2gBIUjfCAV6P6TgT1/aaQKcmuAEC4OZTV1I4EWQLz2gxZw76atuVyvHhTxvi0Flw=="
     },
-    "exeunt": {
-      "version": "1.1.0",
-      "resolved": "https://registry.npmjs.org/exeunt/-/exeunt-1.1.0.tgz",
-      "integrity": "sha512-dd++Yn/0Fp+gtJ04YHov7MeAii+LFivJc6KqnJNfplzLVUkUDrfKoQDTLlCgzcW15vY5hKlHasWeIsQJ8agHsw==",
-      "dev": true
-    },
     "exit": {
       "version": "0.1.2",
       "resolved": "https://registry.npmjs.org/exit/-/exit-0.1.2.tgz",

services/track-changes/package.json

@@ -26,6 +26,7 @@
     "aws-sdk": "^2.643.0",
     "body-parser": "^1.19.0",
     "bson": "^1.1.5",
+    "bunyan": "^1.8.15",
     "byline": "^5.0.0",
     "express": "4.17.1",
     "heap": "^0.2.6",
@@ -42,7 +43,6 @@
   },
   "devDependencies": {
     "babel-eslint": "^10.1.0",
-    "bunyan": "~2.0.2",
     "chai": "~4.2.0",
     "cli": "^1.0.1",
     "eslint": "^6.8.0",