Merge branch 'mahf708/eamxx/rcs-dask-hotfix' (PR #7868)

This pull request makes a small update to the dependency checks
in rcs_stats.py by ensuring that the dask library is available
before running the script.

This is similar to how other required libraries are handled.

[BFB]

Author: bartgol

components/eamxx/cime_config/SystemTests/rcs_stats.py

@@ -67,6 +67,7 @@
     from utils import _ensure_pylib_impl
 
     _ensure_pylib_impl("xarray")
+    _ensure_pylib_impl("dask")
     _ensure_pylib_impl("scipy")
     _ensure_pylib_impl("statsmodels", min_version="0.14.0")