add backslash for internalNamespaces

Without backslash,  classes begin with these words can’t be loaded.

[loadClass Method in AopComposerLoader](https://github.com/chuck911/go-aop-php/blob/600939d31449a5a46cc8e05ab06b7f1d7bfd3079/src/Go/Instrument/ClassLoading/AopComposerLoader.php#L88-L101) :
```
public function loadClass($class)
{
    if ($file = $this->original->findFile($class)) {
        $isInternal = false;
        foreach ($this->internalNamespaces as $ns) {
            if (strpos($class, $ns) === 0) {
                $isInternal = true;
                break;
            }
        }

        include ($isInternal ? $file : FilterInjectorTransformer::rewrite($file));
    }
}
```