Remove temp index on job artifacts

What does this MR do?

We needed this index to run migration 20200809221641_migrate_license_management_artifacts_to_license_scanning Since this migration is rolled up, we can remove the index

This index is added in this migration

Issue: #233387 (closed)

Migratiom

up

➜  gitlab git:(233387-remove-lc-temp-index) ✗ rails db:migrate 
== 20201019130244 RemoveLicenseComplianceTempIndex: migrating =================
-- transaction_open?()
   -> 0.0000s
-- indexes(:ci_job_artifacts)
   -> 0.0049s
-- execute("SET statement_timeout TO 0")
   -> 0.0002s
-- remove_index(:ci_job_artifacts, {:algorithm=>:concurrently, :name=>"index_ci_job_artifacts_on_license_compliance_file_types"})
   -> 0.0055s
-- execute("RESET ALL")
   -> 0.0002s
== 20201019130244 RemoveLicenseComplianceTempIndex: migrated (0.0113s) ========

down

== 20201019130244 RemoveLicenseComplianceTempIndex: reverting =================
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:ci_job_artifacts, [:job_id, :file_type], {:where=>"file_type = 10 OR file_type = 101", :name=>"index_ci_job_artifacts_on_license_compliance_file_types", :algorithm=>:concurrently})
   -> 0.0042s
-- execute("SET statement_timeout TO 0")
   -> 0.0001s
-- add_index(:ci_job_artifacts, [:job_id, :file_type], {:where=>"file_type = 10 OR file_type = 101", :name=>"index_ci_job_artifacts_on_license_compliance_file_types", :algorithm=>:concurrently})
   -> 0.0071s
-- execute("RESET ALL")
   -> 0.0002s
== 20201019130244 RemoveLicenseComplianceTempIndex: reverted (0.0120s) ========

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #233387 (closed)