chore: Unify "node:" prefixes in code examples (#6532)

Author: damianstasik

pages/en/learn/manipulating-files/nodejs-file-stats.md

@@ -22,7 +22,7 @@ fs.stat('/Users/joe/test.txt', (err, stats) => {
 ```
 
 ```mjs
-import fs from 'node:fs/promises';
+import fs from 'node:fs';
 
 fs.stat('/Users/joe/test.txt', (err, stats) => {
   if (err) {
@@ -45,7 +45,7 @@ try {
 ```
 
 ```mjs
-import fs from 'node:fs/promises';
+import fs from 'node:fs';
 
 try {
   const stats = fs.statSync('/Users/joe/test.txt');

pages/en/learn/manipulating-files/reading-files-with-nodejs.md

@@ -21,7 +21,7 @@ fs.readFile('/Users/joe/test.txt', 'utf8', (err, data) => {
 ```
 
 ```mjs
-import fs from 'node:fs/promises';
+import fs from 'node:fs';
 
 fs.readFile('/Users/joe/test.txt', 'utf8', (err, data) => {
   if (err) {

pages/en/learn/manipulating-files/working-with-file-descriptors-in-nodejs.md

@@ -19,7 +19,7 @@ fs.open('/Users/joe/test.txt', 'r', (err, fd) => {
 ```
 
 ```mjs
-const fs = require('node:fs');
+import fs from 'node:fs';
 
 fs.open('/Users/joe/test.txt', 'r', (err, fd) => {
   // fd is our file descriptor

pages/en/learn/modules/backpressuring-in-streams.md

@@ -600,7 +600,7 @@ myReadableStream.on('data', chunk => {
 ```
 
 ```mjs
-import { Readable } from 'stream';
+import { Readable } from 'node:stream';
 
 // Create a custom Readable stream
 const myReadableStream = new Readable({