Revert "UniStore: Add folder to the SQL backend" (#95966)

Revert "UniStore: Add folder to the SQL backend (#95671)"

This reverts commit f075662696.

pkg/storage/unified/sql/testdata/mysql--resource_update-single path.sql

@@ -2,7 +2,6 @@ UPDATE `resource`
     SET
         `guid`   = '',
         `value`  = '[]',
-        `folder`  = 'fldr',
         `action` = 'UNKNOWN'  
     WHERE 1 = 1
         AND `group`     = 'gg'