Remove columns that were used for terraform state replication

What does this MR do?

Remove columns used in the original replication of terraform states (not released)

Relates to: #258262 (closed)

Database Review

Column Ignores (In 13.5): https://gitlab.com/gitlab-org/gitlab/-/blob/v13.5.0-ee/app/models/terraform/state.rb#L10

Number of rows in the table: 2262

Up:

== 20201103013242 RemoveTerraformStateVerificationColumns: migrating ==========
-- transaction()
-- remove_column(:terraform_states, :verification_retry_at, :datetime_with_timezone)
   -> 0.0031s
-- remove_column(:terraform_states, :verified_at, :datetime_with_timezone)
   -> 0.0009s
-- remove_column(:terraform_states, :verification_retry_count, :integer, {:limit=>2})
   -> 0.0009s
-- remove_column(:terraform_states, :verification_checksum, :binary, {:using=>"verification_checksum::bytea"})
   -> 0.0008s
-- remove_column(:terraform_states, :verification_failure, :text)
   -> 0.0010s
   -> 0.0078s
== 20201103013242 RemoveTerraformStateVerificationColumns: migrated (0.0078s) =

Down:

== 20201103013242 RemoveTerraformStateVerificationColumns: reverting ==========
-- column_exists?(:terraform_states, :verification_retry_at)
   -> 0.0021s
-- add_column(:terraform_states, :verification_retry_at, :datetime_with_timezone)
   -> 0.0013s
-- column_exists?(:terraform_states, :verified_at)
   -> 0.0009s
-- add_column(:terraform_states, :verified_at, :datetime_with_timezone)
   -> 0.0010s
-- column_exists?(:terraform_states, :verification_retry_count)
   -> 0.0009s
-- add_column(:terraform_states, :verification_retry_count, :integer, {:limit=>2})
   -> 0.0009s
-- column_exists?(:terraform_states, :verification_checksum)
   -> 0.0009s
-- add_column(:terraform_states, :verification_checksum, :binary, {:using=>"verification_checksum::bytea"})
   -> 0.0012s
-- column_exists?(:terraform_states, :verification_failure)
   -> 0.0008s
-- add_column(:terraform_states, :verification_failure, :text)
   -> 0.0009s
-- transaction_open?()
   -> 0.0000s
-- current_schema()
   -> 0.0001s
-- execute("ALTER TABLE terraform_states\nADD CONSTRAINT check_21a47163ea\nCHECK ( char_length(verification_failure) <= 255 )\nNOT VALID;\n")
   -> 0.0010s
-- current_schema()
   -> 0.0002s
-- execute("SET statement_timeout TO 0")
   -> 0.0004s
-- execute("ALTER TABLE terraform_states VALIDATE CONSTRAINT check_21a47163ea;")
   -> 0.0007s
-- execute("RESET ALL")
   -> 0.0004s
== 20201103013242 RemoveTerraformStateVerificationColumns: reverted (0.0254s) =

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