fix(generator): prevent copied syntaxes from being syntaxes child dir

[Yokozuna59]

When executing the copy:monarch-syntax script, it performs the following:

public/
├── ...
├── syntaxes/                       # old from HelloWorld example
│   ├── language.monarch.js         # old from HelloWorld example
│   ├── language.monarch.js.map     # old from HelloWorld example
│   │
│   └── syntaxes/                   # new from actual grammar
│       ├── language.monarch.js     # new from actual grammar
│       └── language.monarch.js.map # new from actual grammar
└── ...

Whereas is should be:

public/
├── ...
├── syntaxes/                   # new from actual grammar
│   ├── language.monarch.js     # new from actual grammar
│   └── language.monarch.js.map # new from actual grammar
└── ...

[msujew]

Looks good to me, thanks 👍