extension.toml repository URL points to miden-lsp instead of zed-extension

The Zed extension metadata currently points the top-level `repository` field at:

```toml
repository = "https://github.com/0xMiden/miden-lsp"
```

but this extension lives in `0xMiden/zed-extension`.

That can send users or extension tooling to the language server repository when they are looking for the Zed extension source. The grammar-specific `tree-sitter-masm` repository entry should stay as-is; only the top-level extension repository metadata needs to point at this repo.