update: fix error handling assertion in DecisionServiceTest to correctly verify error state

Author: FarhanAnjum-opti

core-api/src/test/java/com/optimizely/ab/bucketing/DecisionServiceTest.java

@@ -1554,7 +1554,7 @@ public void getVariationCmabExperimentServiceError() {
         assertNull(result.getResult());
 
         // Verify that the error is not propagated (no exception thrown)
-        assertFalse(result.isError());
+        assertTrue(result.isError());
 
         // Assert that CmabService.getDecision was called exactly once
         verify(mockCmabService, times(1)).getDecision(any(), any(), any(), any());