try smaller fix

Author: staabm

src/Analyser/MutatingScope.php

@@ -150,7 +150,6 @@
 use function array_values;
 use function count;
 use function explode;
-use function function_exists;
 use function get_class;
 use function implode;
 use function in_array;
@@ -161,7 +160,6 @@
 use function ltrim;
 use function md5;
 use function sprintf;
-use function str_increment;
 use function str_starts_with;
 use function strlen;
 use function strtolower;
@@ -1739,11 +1737,7 @@ static function (Node $node, Scope $scope) use ($arrowScope, &$arrowFunctionImpu
 						if ($varValue === '') {
 							$varValue = '1';
 						} elseif (!is_bool($varValue)) {
-							if (function_exists('str_increment') && is_string($varValue)) {
-								$varValue = str_increment($varValue);
-							} else {
-								++$varValue;
-							}
+							++$varValue;
 						}
 					} elseif (is_numeric($varValue)) {
 						--$varValue;