try smaller fix

Author: staabm

src/Analyser/MutatingScope.php

@@ -1739,11 +1739,7 @@ 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;