panic in load embedded ruleguard rules: can't load fmt

I was trying out the latest v0.6.0 (https://github.com/go-critic/go-critic/releases/tag/v0.6.0) on Windows and it failed with:

```
> gocritic ./...
panic: load embedded ruleguard rules: rules/rules.go:13: can't load fmt

goroutine 1 [running]:
github.com/go-critic/go-critic/checkers.init.9()
        /home/isharipov/CODE/go-critic3/checkers/checkers.go:47 +0x3b4
```