[Bug]: The RegExp constructor does not raise a SyntaxError for octal escapes in Unicode mode

### ChakraCore Version

36becec

### Steps to reproduce

When using the `RegExp` constructor to create a regular expression with the `u` flag, if the pattern contains an octal escape sequence , the engine does not raise a `SyntaxError` according to the specification, but silently returns an invalid regular expression object. This behavior violates the ECMAScript standard.

### Proof of concept

```js
print(RegExp('[\\03]', 'u'));
```

### Exception or Error

```text
/[\03]/u
```

### Additional Context

The expected output should throw "SyntaxError".