Fix the issue where switching operators in a relationship field filter causes duplicate options to appear in the dropdown.
### Describe the Bug **Description** Opening a relationship field filter in the list view and switching the operator from `equals` to `is in` causes duplicate options to appear in the value dropdown ### Link to the code that reproduces this issue https://github.com/zubricks/where-builder-repro ### Reproduction Steps 1. Go to the Products list view → open a filter → select the category field with equals operator → select a value 2. Change the operator to is in 3. Open the value dropdown — duplicate entries appear ### Which area(s) are affected? area: core ### Environment Info ```text Binaries: Node: 23.11.0 npm: 11.4.2 Yarn: N/A pnpm: 10.10.0 Relevant Packages: payload: 3.79.0 next: 15.4.11 @payloadcms/db-postgres: 3.79.0 @payloadcms/drizzle: 3.79.0 @payloadcms/graphql: 3.79.0 @payloadcms/next/utilities: 3.79.0 @payloadcms/richtext-lexical: 3.79.0 @payloadcms/translations: 3.79.0 @payloadcms/ui/shared: 3.79.0 react: 19.2.1 react-dom: 19.2.1 ```