gencpp: 0.4.17-0 in 'groovy/distribution.yaml' [bloom]

Increasing version of package(s) in repository `gencpp` to `0.4.17-0`:

- distro file: `groovy/distribution.yaml`
- bloom version: `0.5.1`
- previous version for package: `0.4.14-0`

## gencpp

```
* revert "python 3 compatibility" (introduced in 0.4.15)
```