Bug#908662: r-cran-etm: autopkgtest regression: saved results mismatch

[Graham Inggs]

Control: severity -1 important

Downgrading severity, since the autopkgtests now pass in unstable [1],
to avoid autoremoval warnings in several other packages.

[1] https://ci.debian.net/packages/r/r-cran-etm/unstable/amd64/