EA doesn't recommend uninstalling using this method, so I did it at my own risk. Seems to run smooth for me, although might not be the same for everyone else.
To Uninstall a Pack, just find a folder where all your Origin Games are installed, open The Sims 4 folder and delete a Pack folder of your choice.
My Example:
GP01 – Outdoor Retreat Game Pack
EP01 – Get To Work Expansion Pack
You have to know which pack is which, so you can remove the correct one. I don't delete it, i just move the folder to my desktop. When I am done with the challenge, then I move the folder back.