Update documentation for OWC

I think the documentation section on OWC:
https://argopy.readthedocs.io/en/latest/advanced-tools/quality_control/salinity.html
needs to be updated for a better integration with the JSON config file of ``pyowc``:
```python
USER_CONFIG = owc.configuration.load() # fetch the default configuration and parameters
```

Start with the OWC section on the linked salinity documentation page and review the shown pyowc USER_CONFIG loading example. Update the documentation to explain the integration with pyowc's JSON configuration file, and consider the work done when the example and surrounding guidance accurately describe that setup.

Written by the indexing model from the issue text.