Increase max backup size (#12602)

* Increased max backup size

* partially reverted schema.rb

db/migrate/20191212003415_increase_backup_size.rb

@@ -0,0 +1,9 @@
+class IncreaseBackupSize < ActiveRecord::Migration[5.2]
+  def up
+    change_column :backups, :dump_file_size, :bigint
+  end
+
+  def down
+    change_column :backups, :dump_file_size, :integer
+  end
+end