docs: replace var with let and const in rule examples (#19515)

Author: Tanujkanti4441

docs/src/rules/no-caller.md

@@ -8,7 +8,7 @@ The use of `arguments.caller` and `arguments.callee` make several code optimizat
 
 ```js
 function foo() {
-    var callee = arguments.callee;
+    const callee = arguments.callee;
 }
 ```
 

docs/src/rules/no-delete-var.md

@@ -20,7 +20,7 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-delete-var: "error"*/
 
-var x;
+let x;
 delete x;
 ```
 

docs/src/rules/no-extend-native.md

@@ -15,13 +15,13 @@ For example here we are overriding a builtin method that will then affect all Ob
 Object.prototype.extra = 55;
 
 // loop through some userIds
-var users = {
+const users = {
     "123": "Stan",
     "456": "David"
 };
 
 // not what you'd expect
-for (var id in users) {
+for (const id in users) {
     console.log(id); // "123", "456", "extra"
 }
 ```
@@ -68,7 +68,7 @@ Object.prototype.a = "a";
 This rule *does not* report any of the following less obvious approaches to modify the prototype of builtin objects:
 
 ```js
-var x = Object;
+const x = Object;
 x.prototype.thing = a;
 
 eval("Array.prototype.forEach = 'muhahaha'");

docs/src/rules/no-extra-bind.md

@@ -11,7 +11,7 @@ further_reading:
 The `bind()` method is used to create functions with specific `this` values and, optionally, binds arguments to specific values. When used to specify the value of `this`, it's important that the function actually uses `this` in its function body. For example:
 
 ```js
-var boundGetName = (function getName() {
+const boundGetName = (function getName() {
     return this.name;
 }).bind({ name: "ESLint" });
 
@@ -24,7 +24,7 @@ Sometimes during the course of code maintenance, the `this` value is removed fro
 
 ```js
 // useless bind
-var boundGetName = (function getName() {
+const boundGetName = (function getName() {
     return "ESLint";
 }).bind({ name: "ESLint" });
 
@@ -46,25 +46,25 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-extra-bind: "error"*/
 
-var x = function () {
+const x = function () {
     foo();
 }.bind(bar);
 
-var x = (() => {
+const y = (() => {
     foo();
 }).bind(bar);
 
-var x = (() => {
+const z = (() => {
     this.foo();
 }).bind(bar);
 
-var x = function () {
+const a = function () {
     (function () {
       this.foo();
     }());
 }.bind(bar);
 
-var x = function () {
+const b = function () {
     function foo() {
       this.bar();
     }
@@ -80,11 +80,11 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-extra-bind: "error"*/
 
-var x = function () {
+const x = function () {
     this.foo();
 }.bind(bar);
 
-var x = function (a) {
+const y = function (a) {
     return a + 1;
 }.bind(foo, bar);
 ```

docs/src/rules/no-global-assign.md

@@ -57,7 +57,7 @@ Examples of **correct** code for this rule:
 /*eslint no-global-assign: "error"*/
 
 a = 1
-var b = 1
+let b = 1
 b = 2
 ```