Bug#1050832: sarsen: autopkgtest needs update for python-xarray 2023.08.0

[Graham Inggs]

Control: severity -1 serious
Control: tags -1 + ftbfs

As can be seen on reproducible builds [1], this same error causes
sarsen to FTBFS in unstable.


[1] https://tests.reproducible-builds.org/debian/rb-pkg/sarsen.html