Revert "Merge pull request #16254 from zuhao/refactor_activerecord_attribute_decorators_test"

This reverts commit 16fe19831548f108c113094d106663497fc190d5, reversing
changes made to 4c81c8ce533896be28bdc0b055ff30bb9dee1316.

The call to `Model.reset_column_information` was to express the intent of the test.
`reset_column_information` itself can trigger SQL queries because it checks
for a tables existance. Let's move it outside of the block.

/cc @sgrif