Fix example for randomKey() (#25)

Author: martinsoenen

content/2.extensions/array.md

@@ -12,11 +12,5 @@ $faker->randomElement(['first', 'second', 'third', 'fourth']); // second
 ## Random Key
 
 ```php
-$faker->randomKey([['firstname' => 'John'], ['lastname' => 'Doe'], ['nickname' => 'Johnny'], ['login' => 'j.doe']]); // nickname
-```
-
-## Random Key Number
-
-```php
-$faker->randomKeyNumber([['firstname' => 'John'], ['lastname' => 'Doe'], ['nickname' => 'Johnny'], ['login' => 'j.doe']]); // 2
+$faker->randomKey(['firstname' => 'John', 'lastname' => 'Doe', 'nickname' => 'Johnny', 'login' => 'j.doe']); // nickname
 ```