deps: bump github.com/dropbox/dropbox-sdk-go-unofficial/v6 from 6.3.0 to 6.4.0 in the go-dependencies group across 1 directory

deps: bump github.com/dropbox/dropbox-sdk-go-unofficial/v6 from 6.3.0 to 6.4.0 in the go-dependencies group across 1 directory #79