Improve worker module docstring

Corrected grammatical error and improved the wording of module docstring in
`make_CHS_currents_file.py` and its associated tests. Ensured consistent use of
terminology by changing "average" to "averages" and specifying "netCDF" instead
of "nc file".

nowcast/workers/make_CHS_currents_file.py

@@ -12,8 +12,8 @@
 #  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
-"""SalishSeaCast worker that average, unstaggers and rotates the near surface velocities,
-and writes them out in an nc file for CHS to use
+"""SalishSeaCast worker that averages, unstaggers and rotates the near surface velocities,
+and writes them out in a netCDF file for CHS to use.
 """
 import logging
 import os

tests/workers/test_make_CHS_currents_file.py

@@ -76,7 +76,7 @@ def test_instantiate_worker(self, mock_worker):
         worker = make_CHS_currents_file.main()
         assert worker.name == "make_CHS_currents_file"
         assert worker.description.startswith(
-            "SalishSeaCast worker that average, unstaggers and rotates the near surface velocities,"
+            "SalishSeaCast worker that averages, unstaggers and rotates the near surface velocities,"
         )
 
     def test_add_run_type_arg(self, mock_worker):