return value of `Type.String()` for function type doesn't match Go's `reflect` pkg

Return value of `Type.String()` for function type doesn't match equivalent call using Go's `reflect` package.

The code snippet below produces:
- tinygo: `func`
- go1.22: `func(int, string) (bool, error)`

```Go
f := func(int, string) (bool, error) {
	return false, nil
}
rt := reflect.TypeOf(f)
fmt.Println(rt.String()) 
```