fix(deps): Move @types/express to dependencies (#457)

Author: koistya

package-lock.json

@@ -13,6 +13,7 @@
     "./testing": "./build/src/testing.js"
   },
   "dependencies": {
+    "@types/express": "4.17.13",
     "body-parser": "^1.18.3",
     "cloudevents": "^6.0.0",
     "express": "^4.16.4",
@@ -47,7 +48,6 @@
   "devDependencies": {
     "@microsoft/api-extractor": "^7.18.20",
     "@types/body-parser": "1.19.2",
-    "@types/express": "4.17.13",
     "@types/minimist": "1.2.2",
     "@types/mocha": "9.0.0",
     "@types/node": "14.18.11",