expect_doppleganger throws warnings due to expect_snapshot_file deprecation of binary arg

[arnaud-feldmann]

Hi @lionel- ,

Hope you're doing well,

As it is stated in my title, expect_doppleganger throws a warning because of the deprecation of binary arg of testthat::expect_snapshot_file.

As you've done both commits, it is likely that you're aware of the issue. Through, in your master branch of vdiffr, it seems like the binary arg of testthat::expect_snapshot_file is still called.

Keep up the good work !

[lionel-]

I forgot about that and the warning didn't surface in vdiffr tests :(

Thanks!