Update dependency @nestjs/swagger to v4

Author: renovate-bot

backend/package-lock.json

@@ -25,7 +25,7 @@
     "@nestjs/jwt": "6.1.1",
     "@nestjs/passport": "6.1.0",
     "@nestjs/platform-express": "6.5.3",
-    "@nestjs/swagger": "3.1.0",
+    "@nestjs/swagger": "4.5.8",
     "@nestjs/typeorm": "6.1.3",
     "bcrypt": "3.0.6",
     "class-transformer": "0.2.3",