Remove denodeify

We've had promise-based file system functions for an age.

package.json

@@ -14,7 +14,6 @@
     "@dotcom-reliability-kit/logger": "^3.0.3",
     "@dotcom-reliability-kit/serialize-request": "^3.0.1",
     "@financial-times/n-flags-client": "^15.0.0",
-    "denodeify": "^1.2.1",
     "express": "^4.17.3",
     "isomorphic-fetch": "^3.0.0",
     "n-health": "^13.0.0",

src/lib/instrument-listen.js

@@ -4,14 +4,11 @@ const metrics = require('next-metrics');
 const logger = require('@dotcom-reliability-kit/logger');
 const http = require('http');
 const https = require('https');
-const denodeify = require('denodeify');
 const path = require('path');
+const {readFile} = require('fs/promises');
 const {STATUS_CODES} = http;
 const serializeRequest = require('@dotcom-reliability-kit/serialize-request');
 
-const fs = require('fs');
-const readFile = denodeify(fs.readFile);
-
 module.exports = class InstrumentListen {
 	constructor (app, meta, initPromises) {
 		this.app = app;

tsconfig.json

@@ -1,5 +1,5 @@
 {
-  "extends": "@tsconfig/node12/tsconfig.json",
+  "extends": "@tsconfig/node18/tsconfig.json",
   "compilerOptions": {
     "allowJs": true,
     "checkJs": true,