bug #4533 Revert PHP7.4 - Add "str_split" => "mb_str_split" mapping (keradus)

This PR was squashed before being merged into the 2.12 branch (closes #4533).

Discussion
----------

Revert PHP7.4 - Add "str_split" => "mb_str_split" mapping

Reverts #4380
Closes #4529

Commits
-------

d35c431 Revert PHP7.4 - Add \"str_split\" => \"mb_str_split\" mapping

Author: keradus

src/Fixer/Alias/MbStrFunctionsFixer.php

@@ -28,7 +28,6 @@ final class MbStrFunctionsFixer extends AbstractFunctionReferenceFixer
      * @var array the list of the string-related function names and their mb_ equivalent
      */
     private static $functionsMap = [
-        'str_split' => ['alternativeName' => 'mb_str_split', 'argumentCount' => [1, 2, 3]],
         'stripos' => ['alternativeName' => 'mb_stripos', 'argumentCount' => [2, 3]],
         'stristr' => ['alternativeName' => 'mb_stristr', 'argumentCount' => [2, 3]],
         'strlen' => ['alternativeName' => 'mb_strlen', 'argumentCount' => [1]],
@@ -43,23 +42,6 @@ final class MbStrFunctionsFixer extends AbstractFunctionReferenceFixer
         'substr_count' => ['alternativeName' => 'mb_substr_count', 'argumentCount' => [2, 3, 4]],
     ];
 
-    /**
-     * @var array<string, array>
-     */
-    private $functions;
-
-    public function __construct()
-    {
-        parent::__construct();
-
-        $this->functions = array_filter(
-            self::$functionsMap,
-            static function (array $mapping) {
-                return \function_exists($mapping['alternativeName']);
-            }
-        );
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -104,7 +86,7 @@ public function isCandidate(Tokens $tokens)
     protected function applyFix(\SplFileInfo $file, Tokens $tokens)
     {
         $argumentsAnalyzer = new ArgumentsAnalyzer();
-        foreach ($this->functions as $functionIdentity => $functionReplacement) {
+        foreach (self::$functionsMap as $functionIdentity => $functionReplacement) {
             $currIndex = 0;
             while (null !== $currIndex) {
                 // try getting function reference and translate boundaries for humans

tests/Fixer/Alias/MbStrFunctionsFixerTest.php

@@ -37,7 +37,7 @@ public function testFix($expected, $input = null)
 
     public function provideFixCases()
     {
-        $cases = [
+        return [
             ['<?php $x = "strlen";'],
             ['<?php $x = Foo::strlen("bar");'],
             ['<?php $x = new strlen("bar");'],
@@ -62,18 +62,5 @@ public function strtolower($a);
                 }',
             ],
         ];
-
-        if (\function_exists('mb_str_split')) {
-            $cases[] = [
-                '<?php $a = mb_str_split($a);',
-                '<?php $a = str_split($a);',
-            ];
-        } else {
-            $cases[] = [
-                '<?php $a = str_split($a);',
-            ];
-        }
-
-        return $cases;
     }
 }