Add --quiet flag to NCSO alerts command

Something about the way fabric/ebmbot work means that stderr gets
reported to Slack, interspersed with stdout. This flag disables the
stderr logging to stop the command creating a lot of noise in a Slack.

If there's a simple way to get it just report stdout that would also
solve the problem, but I couldn't immediately see one.

See also:
 * ebmdatalab/openprescribing#4772

ebmbot/job_configs.py

@@ -104,7 +104,7 @@
                 "report_stdout": True,
             },
             "ncso_send_alerts": {
-                "run_args_template": "fab --hide=running,stdout,status call_management_command:send_ncso_concessions_alerts,production",
+                "run_args_template": "fab --hide=running,stdout,status call_management_command:send_ncso_concessions_alerts,production,--quiet",
                 "report_stdout": True,
             },
             "import_measure_definition": {