Remove migration from revert

Removes the dependency_proxy_manifests content-type
migration from the revert.

db/migrate/20210128140157_add_content_type_to_dependency_proxy_manifests.rb

+# frozen_string_literal: true
+
+class AddContentTypeToDependencyProxyManifests < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+
+  # rubocop:disable Migration/AddLimitToTextColumns
+  # limit is added in 20210128140232_add_text_limit_to_dependency_proxy_manifests_content_type.rb
+  def change
+    add_column :dependency_proxy_manifests, :content_type, :text
+  end
+  # rubocop:enable Migration/AddLimitToTextColumns
+end

db/migrate/20210128140232_add_text_limit_to_dependency_proxy_manifests_content_type.rb

+# frozen_string_literal: true
+
+class AddTextLimitToDependencyProxyManifestsContentType < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_text_limit :dependency_proxy_manifests, :content_type, 255
+  end
+
+  def down
+    remove_text_limit :dependency_proxy_manifests, :content_type
+  end
+end

db/schema_migrations/20210128140157

+0fa84b2038f33e27e549bdb3eb137e1813f604b6e81abc67a49a54d3e1e4bcf5
\ No newline at end of file

db/schema_migrations/20210128140232

+93f337364eb5ca5c67f4d4767d1aee9972bfe0596c89f006317dd6103558e35c
\ No newline at end of file

db/structure.sql

@@ -11775,7 +11775,9 @@ CREATE TABLE dependency_proxy_manifests (
     file_name text NOT NULL,
     file text NOT NULL,
     digest text NOT NULL,
+    content_type text,
     CONSTRAINT check_079b293a7b CHECK ((char_length(file) <= 255)),
+    CONSTRAINT check_167a9a8a91 CHECK ((char_length(content_type) <= 255)),
     CONSTRAINT check_c579e3f586 CHECK ((char_length(file_name) <= 255)),
     CONSTRAINT check_f5d9996bf1 CHECK ((char_length(digest) <= 255))
 );