Remove dashboard.json

[andrewazores]

dashboard.json is not used by the jfr-datasource directly. It is intended to be imported into a Grafana Dashboard instance which is also configured with a jfr-datasource instance as a datasource. The Cryostat Grafana Dashboard container image bakes in the dashboard.json already, and any updates to the default Cryostat dashboard should be done there and not here. So, the dashboard.json definition in this project should be removed as it is now obsolete and redundant.

See #38 .