fix(package): update @nestjs/websockets to version 5.3.15

Closes #17

Author: greenkeeper[bot]

package.json

@@ -46,7 +46,7 @@
     "@nestjs/swagger": "^1.1.3",
     "@nestjs/testing": "^4.5.5",
     "@nestjs/typeorm": "^2.0.0",
-    "@nestjs/websockets": "^4.5.8",
+    "@nestjs/websockets": "^5.3.15",
     "@types/dotenv": "^4.0.2",
     "@types/jsonwebtoken": "^7.2.5",
     "@types/node": "^9.3.0",