Bump eslint from 3.19.0 to 6.6.0 in /api

Bumps [eslint](https://github.com/eslint/eslint) from 3.19.0 to 6.6.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v3.19.0...v6.6.0)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

api/package.json

@@ -18,6 +18,6 @@
     "mongoose": "^5.7.8"
   },
   "devDependencies": {
-    "eslint": "^3.19.0"
+    "eslint": "^6.6.0"
   }
 }