Update mongoose to version 6.5.1

Author: depfu[bot]

package.json

@@ -42,7 +42,7 @@
     "jsonwebtoken": "^8.5.1",
     "md5": "^2.3.0",
     "moment": "^2.29.1",
-    "mongoose": "^5.12.8",
+    "mongoose": "^6.5.1",
     "pug": "^2.0.4",
     "redis": "^3.1.2",
     "supertest": "^4.0.2",