rocon_msgs: 0.7.5-2 in 'indigo/distribution.yaml' [bloom]

Increasing version of package(s) in repository `rocon_msgs` to `0.7.5-2`:

- distro file: `indigo/distribution.yaml`
- bloom version: `0.5.2`
- previous version for package: `0.7.3-0`

## rocon_msgs

```
* graveyarding rocon_annotation_msgs (no longer used).
```