Increase csv import user limit

ICP has a limitation that only 1000 users can added to a project at at time via CSV import tool.

HS2 projects typically have circa 3000 members with Deliverables Management permissions.. I've attached an example spreadsheet which I used to import users into an old-style Connected Project.

Moving forward, all new HS2 projects will be using ICP instead of Connect portal. It would be very useful if I could import this many users at once into the new ICP roles via spreadsheet as this process will need to be repeated many times.