Set the 'show advanced option' to '1'
EXEC sp_configure 'show advanced option', '1';
Then run reconfigure:
Then show all configuration options;
Verify that the 'C2 Audit Mode' config_value and run_value fields are set to '1'. If they are - that is what needs to be changed. You should be able to run the code to set the config_value to '0' (disabled).
EXEC sp_configure 'c2 audit mode', '0';
If you run EXEC sp_configure; again it should show the config_value is '0' and the run_value is still '1'. To turn off the c2 audit trace, you need to have the run_value set to '0' as well. To get this, run:
EXEC RECONFIGURE with OVERRIDE;
If that doesn't do it, then restart the SQL SERVER and SQL AGENT services and the config_value will get picked up.