Use built-in gem health check for Solr

[maxkadel]

What maintenance needs to be done?

Change from using a custom health check for Solr to using the built in health check.

Level of urgency

• High
• Moderate
• Low

Why is this maintenance needed?

• We added a Solr health check to the health-monitor-rails gem, and so no longer need a custom health check for Solr

Acceptance criteria

• Remove custom Solr check class
• Configure initializer to use built-in health monitor
• The existing health_check_spec at spec/requests/health_check_spec.rb still passes

Implementation notes, if any

• Make sure to use a string for the Solr url.
• Example config in Orangelight