Set correct format when migrating slides
Slides were still migrated to the text format because the format did not exist in the past for v3.
Related: !264 (merged), !294 (merged), !300 (merged), !311 (merged)
Slides were still migrated to the text format because the format did not exist in the past for v3.
Related: !264 (merged), !294 (merged), !300 (merged), !311 (merged)