fix: packages/serverless-api/package.json to reduce vulnerabilities (#326)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-LODASH-1018905
- https://snyk.io/vuln/SNYK-JS-LODASH-1040724
- https://snyk.io/vuln/SNYK-JS-LODASH-567746
- https://snyk.io/vuln/SNYK-JS-LODASH-590103
- https://snyk.io/vuln/SNYK-JS-LODASH-608086
- https://snyk.io/vuln/SNYK-JS-MARKED-584281
- https://snyk.io/vuln/SNYK-JS-MERGE-1040469
- https://snyk.io/vuln/SNYK-JS-MERGE-1042987
- https://snyk.io/vuln/SNYK-JS-MINIMIST-559764
- https://snyk.io/vuln/SNYK-JS-YARGSPARSER-560381

Co-authored-by: snyk-bot <snyk-bot@snyk.io>

Author: twilio-product-security

packages/serverless-api/package.json

@@ -45,14 +45,14 @@
     "@types/debug": "^4.1.3",
     "@types/jest": "^24.0.16",
     "@types/nock": "^10.0.3",
-    "commitizen": "^3.1.1",
+    "commitizen": "^4.2.4",
     "jest": "^24.8.0",
     "moq.ts": "^6.3.3",
     "nock": "^12.0.3",
     "npm-run-all": "^4.1.5",
     "rimraf": "^2.6.3",
-    "ts-jest": "^24.0.2",
-    "typedoc": "^0.17.4",
+    "ts-jest": "^25.3.0",
+    "typedoc": "^0.18.0",
     "typedoc-plugin-external-module-name": "^3.0.0",
     "typescript": "^3.8.3"
   },