Revert "Increase file upload limit to 128MB"
Revert "Increase file upload limit to 128MB"

This reverts commit 53a988bee01720931455e53803b51bcea10ad10a.

The server crashed trying to upload a 74MB file, so it seems like the limit of 64 MB is right.

OurWorldInData/owid-grapher,OurWorldInData/owid-grapher,owid/owid-grapher,owid/owid-grapher,OurWorldInData/owid-grapher,OurWorldInData/owid-grapher,owid/owid-grapher,OurWorldInData/owid-grapher,owid/owid-grapher,owid/owid-grapher