fix: package.json & yarn.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-BODYPARSER-7926860
- https://snyk.io/vuln/SNYK-JS-EXPRESS-7926867
- https://snyk.io/vuln/SNYK-JS-SEND-7926862
- https://snyk.io/vuln/SNYK-JS-SERVESTATIC-7926865

package.json

@@ -38,7 +38,7 @@
     "convict": "^6.2.4",
     "debug": "^4.3.5",
     "dotenv": "^16.4.5",
-    "express": "^4.19.2",
+    "express": "^4.21.0",
     "ksuid": "^3.0.0",
     "micromatch": "^4.0.7",
     "moment": "^2.30.1",