Bump required npm version to 8.19.4, bump npm dependency to 8.19.4.

package-lock.json is regenerated with npm 8.19.4, which is the version
currently in Node 16.

src/package.json

@@ -53,7 +53,7 @@
     "log4js": "0.6.38",
     "measured-core": "^2.0.0",
     "mime-types": "^2.1.35",
-    "npm": "^6.14.18",
+    "npm": "^8.19.4",
     "openapi-backend": "^5.9.2",
     "proxy-addr": "^2.0.7",
     "rate-limiter-flexible": "^2.4.1",
@@ -94,7 +94,7 @@
   },
   "engines": {
     "node": ">=16.20.1",
-    "npm": ">=6.14.0"
+    "npm": ">=8.19.4"
   },
   "repository": {
     "type": "git",