Delete the vendered grammar/tree-sitter-mojo

[chriselrod]

I'm talking with the maintainer of https://github.com/lsh/tree-sitter-mojo
Now that mojo is 1.0, I think this should get published so packages such as this can use it.

You can also optionally delete it early, and I'll use a fork that carries it and make a far more minimal PR once it gets published.

[yogthos]

Ah ok, we can hold the pr then till it's easier to use :)