doc: removed unnecessary util imports from vm examples

PR-URL: #33179
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc/api/vm.md

@@ -160,7 +160,6 @@ the value of another global variable, then execute the code multiple times.
 The globals are contained in the `context` object.
 
 ```js
-const util = require('util');
 const vm = require('vm');
 
 const context = {
@@ -235,7 +234,6 @@ the code multiple times in different contexts. The globals are set on and
 contained within each individual `context`.
 
 ```js
-const util = require('util');
 const vm = require('vm');
 
 const script = new vm.Script('globalVar = "set"');
@@ -891,7 +889,6 @@ properties but also having the built-in objects and functions any standard
 will remain unchanged.
 
 ```js
-const util = require('util');
 const vm = require('vm');
 
 global.globalVar = 3;
@@ -996,7 +993,6 @@ The following example compiles and executes different scripts using a single
 [contextified][] object:
 
 ```js
-const util = require('util');
 const vm = require('vm');
 
 const contextObject = { globalVar: 1 };
@@ -1092,7 +1088,6 @@ The following example compiles and executes code that increments a global
 variable and sets a new one. These globals are contained in the `contextObject`.
 
 ```js
-const util = require('util');
 const vm = require('vm');
 
 const contextObject = {