Units attribute on anomaly forcing precipitation file is incorrect

[olyson]

The units attribute for the pr variable on the anomaly forcing files is incorrect. It says mm/s, but I think it should be unitless.
E.g. this file:

/glade/campaign/cesm/cesmdata/cseg/inputdata/atm/datm7/anomaly_forcing/CMIP6-SSP1-2.6/af.allvars.CESM.SSP1-2.6.2015-2100_c20220628.nc

[ekluzek]

This seems like a good thing to fix, but maybe a low priority.

[wwieder]

We can hopefully remember to do this correctly when we make anomaly forcing from CESM3 runs. I think this would happen after the code freeze, so changing the milestone.