try not to repot in flowering as this will cause stress to your plants.
However, if your flowering plants are in those really small containers, the sooner the better.

Also keep in mind that cannabis often doubles or triples in size when it flowers out (providing the plants have enough light, nutrients, and room for roots to grow to support this growth).
so use larger containers/pots and flower when the plants ae smaller. this cuts down your veg time and increases the number of harvests you can pull per year.