chore(deps): update dependency mongodb to v6.21.0

Author: renovate[bot]

package.json

@@ -44,7 +44,7 @@
   "resolutions": {
     "rolldown": "1.0.0-beta.60",
     "get-pixels@^3>request": "./external/request",
-    "mongodb": "6.12.0",
+    "mongodb": "6.21.0",
     "pino": "./external/pino",
     "semver": "7.7.3",
     "typescript": "5.9.3",