[Eval > Test Suites] Test case status stays Valid after clearing a Required field value

### EPAM AI DIAL Admin version

Admin: [FE]0.17.0-dev.48 [BE]0.17.0-dev.7

### How to reproduce

1. Login to Admin
2. Navigate to Evaluation - Test Suites
3. Open any existing Test Suite with at least one test case
4. Go to Test Cases tab, click Test Case Schema
5. Add a new field with required toggled on, click Apply
6. Click Save - verify test case status shows Invalid (required field is empty)
7. Fill in a value for the required field, click Save - verify status shows Valid
8. Clear the value from the required field, click Save

### Actual result

Test case status remains Valid after clearing the required field value and saving.

### Expected result

Test case status should change back to Invalid when a required field has no value and the suite is saved.

### Additional information

_No response_

### Confidential information

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