chore: update AdminJS to v6

BREAKING CHANGE: This package version should be used with AdminJS v6

Author: dziraf

package.json

@@ -21,7 +21,7 @@
     }
   },
   "peerDependencies": {
-    "adminjs": ">=5.0.0"
+    "adminjs": ">=6.0.0"
   },
   "optionalDependencies": {
     "@google-cloud/storage": "^5.3.0",
@@ -38,7 +38,7 @@
     "@types/sinon-chai": "^3.2.4",
     "@typescript-eslint/eslint-plugin": "^3.7.0",
     "@typescript-eslint/parser": "^3.7.0",
-    "adminjs": "^5.0.0",
+    "adminjs": "^6.0.0",
     "aws-sdk": "^2.728.0",
     "chai": "^4.2.0",
     "eslint": "^7.5.0",