Pim 3247: Fix pager bug on variant groups

When you were on the variant group page, you could only see 4 variant groups but there were 6 variant groups in reality. 

| Q                    | A
| -------------------- | ---
| Bug fix?             | Yes
| New feature?         | No
| BC breaks?           | No
| CI currently passes? | running
| Tests pass?          | yes
| Scenarios pass?      | running
| Checkstyle issues?*  | No
| PMD issues?**        | No
| Changelog updated?   | Yes
| Fixed tickets        | PIM-3247
| DB schema updated?   | No
| Migration script?    | No
| Doc PR               | No