chore: Delete unused metric models

[feng-tao]

Signed-off-by: feng-tao fengtao04@gmail.com

Summary of Changes

We don't use the metric model for dashboard feature. The model was checked-in way before dashboard feature was designed.

Tests

What tests did you add or modify and why? If no tests were added or modified, explain why. Remove this line

Documentation

What documentation did you add or modify and why? Add any relevant links then remove this line

CheckList

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[allisonsuarez]

thanks! had no idea this existed