Drop autodoc mocks for nemo_nowcast workers

The NEMO_Nowcast package is now installed in the readthedocs build environment.
So, autodoc mocks for its imports are no longer required. Removing those mocks
silences warnings about mocked objects and missing attributes for the
`clear_checklist` and `rotate_logs` worker docs.

docs/conf.py

@@ -86,10 +86,6 @@
     "moad_tools.places",
     "mpl_toolkits.basemap",
     "nemo_cmd",
-    "nemo_nowcast.fileutils",
-    "nemo_nowcast.workers",
-    "nemo_nowcast.workers.clear_checklist",
-    "nemo_nowcast.workers.rotate_logs",
     "netCDF4",
     "OPPTools",
     "pandas",