fix(TreeCascadeDropdownQuestion): fix incorrect options displayed in custom dropdown

[MyvTsv]

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !44958
• TreeCascadeDropdown questions that used a custom dropdown menu were displaying incorrect values. Since all values for custom dropdown menus are stored in the same “glpi_dropdowns_dropdowns” table, the query returned all values instead of filtering based on the itemtype of the selected custom dropdown menu item.

Screenshots (if appropriate):

Before:

After: