PIM-2905 Removed mimetype validation

| Q                    | A
| -------------------- | ---
| Bug fix?             | yes
| New feature?         | no
| BC breaks?           | no
| CI currently passes? | yes
| Tests pass?          | yes
| Scenarios pass?      | yes
| Checkstyle issues?   | no
| Changelog updated?   | yes
| Fixed tickets        | PIM-2905
| Doc PR               |