Adjusted seperator of the `grouped_by_three` formatter.

The spaces around the `repository_dossier_seperator` should be removed for the `groupped_by_three` formatter. Therefore i put the spaces in to the separator itself, so it works for both (`dotted` and `groupped_by_three`)

`dotted` (is unmodified):
`OG 5.7.3.2 / 4.6.2`

`grouped_by_three`:
`OG 573.2 - 4.6.2` --> `OG 573.2-4.6.2`