fix: add locale support to relationship filter options in WhereBuilder (#11783)

### What?

This PR fixes a bug in the relationship filter UI where no options are
displayed when working in a non-default locale with localized
collections. The query to fetch relationship options wasn't including
the current locale parameter, causing the select dropdown to appear
empty.

### Why?

When using localized collections with relationship fields:
1. If you create entries (e.g., Categories) only in a non-default locale
2. Set the global locale to that non-default locale
3. Try to filter another collection by its relationship to those
Categories

The filter dropdown would be empty, despite Categories existing in that
locale. This was happening because the `loadOptions` method in the
RelationshipFilter component didn't include the current locale in its
query.

### How?

The fix is implemented in
`packages/ui/src/elements/WhereBuilder/Condition/Relationship/index.tsx`
by:
1. Adding the `useLocale` hook to get the current locale in the
RelationshipFilter component
2. Including this locale in the query parameters when fetching
relationship options

![Before: Dropdown showing relationship options as empty
options](https://github.com/user-attachments/assets/b796840b-9001-4f38-98c4-7b37ee4121d7)

![After: Dropdown properly showing relationship options in non-default
locale](https://github.com/user-attachments/assets/a2f58d52-881e-49f7-b4dd-4b4ec7d07f10)

Fixes #11782 
Discussion:
https://discord.com/channels/967097582721572934/1350888604150534164

Author: nachomglz