Remove `severity` from monitoring error

[MGaetan89]

Pull request

Description

Remove the severity field from the monitoring Error message.

Changes made

• Self-explanatory.

Checklist

• [ ] APIs have been properly documented (if relevant).
• [ ] The documentation has been updated (if relevant).
• [ ] New unit tests have been written (if relevant).
• [ ] The demo has been updated (if relevant).

[github-actions[bot]]

Code Coverage

Overall Project	48.12%	🟢

Module	Coverage
:pillarbox-player	57.44%	🟢

Files

|Module|File|Coverage|| |:-|:-|:-|:-:| |:pillarbox-player|[Monitoring.kt](https://github.com/SRGSSR/pillarbox-android/blob/f9d17cca91c1d8021b2e191d939ee041c8e4577d/pillarbox-player%2Fsrc%2Fmain%2Fjava%2Fch%2Fsrgssr%2Fpillarbox%2Fplayer%2Fmonitoring%2FMonitoring.kt)|88.99%|🟢| ||[ErrorMessageData.kt](https://github.com/SRGSSR/pillarbox-android/blob/f9d17cca91c1d8021b2e191d939ee041c8e4577d/pillarbox-player%2Fsrc%2Fmain%2Fjava%2Fch%2Fsrgssr%2Fpillarbox%2Fplayer%2Fmonitoring%2Fmodels%2FErrorMessageData.kt)|43.33%|🟢|