Remove health_status column from epics

What does this MR do?

It removes the health_status column from the db.

Related issues and MRs

• Removing health_status related code from epics: !25995 (merged)
• Ignoring the column in the model: !26763 (merged)
• Follow-up issue to remove ignore_column: #209749 (closed)

Migration output

Up

== 20200226124757 RemoveHealthStatusFromEpics: migrating ======================
-- remove_column(:epics, :health_status, :integer, {:limit=>2})
   -> 0.0016s
== 20200226124757 RemoveHealthStatusFromEpics: migrated (0.0046s) =============

Down

== 20200226124757 RemoveHealthStatusFromEpics: reverting ======================
-- add_column(:epics, :health_status, :integer, {:limit=>2})
   -> 0.0020s
== 20200226124757 RemoveHealthStatusFromEpics: reverted (0.0131s) =============

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• [-] Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• Database guides
• [-] Separation of EE specific content