Drop InfluxDB/Grafana support for the GithubUsageTracker

[Fryguy]

We don't currently use it, so it is just a maintenance burden. If we want to resurrect we can always revert this PR.

@bdunne Please review.

[miq-bot]

Checked commit https://github.com/Fryguy/miq_bot/commit/c8027f10f76ad7e6d3cf81ac1b0a07dcac6b9e3a with ruby 2.6.10, rubocop 1.28.2, haml-lint 0.35.0, and yamllint 3 files checked, 1 offense detected

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• [ ] :bomb: :boom: :fire: :fire_engine: - Linter/Yaml - missing config files