[CodeQuality] For to foreach where useful

[TomasVotruba]

-for ($i = 0, $c = count($tokens); $i < $c; ++$i) {
+foreach ($tokens as $i => $token) {
            if ($token[0] === T_STRING && $token[1] === 'fn') {
                $previousNonSpaceToken = $this->getPreviousNonSpaceToken($tokens, $i);
                if ($previousNonSpaceToken !== null && $previousNonSpaceToken[0] === T_OBJECT_OPERATOR) {
                    continue;
                }
                $tokens[$i][0] = self::T_FN;
            }
        }