fix: update Grafana dashboard to reflect throttle metrics rename

[squat]

The metrics for throttling reasons have been renamed from nvidia_smi_clocks_throttle_reasons_* to nvidia_smi_clocks_event_reasons_*. This change has broken the Grafana dashboard.

xref: #123

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[utkuozdemir]

Thank you for the contribution. One thing though - I think it makes more sense to evolve the Grafana dashboard in a way that it would work both with old and new naming, so we keep it backward-compatible. Can you make it fallback to the old metric if the new metric is not there (I think there was a way to do that, but don't remember how).