Update TestValidation/Homogeneous_Aggregate_Validation_test_6

[polds]

TestValidation/Homogeneous_Aggregate_Validation_test_6 is broken. We should fix or remove.

=== RUN   TestValidation/Homogeneous_Aggregate_Validation_test_6
    eval_test.go:359: Compile() got error = unexpected token Operator("?") (1:10)
         | name in [?optional.ofNonZeroValue(''), 'hello', ?optional.of('')]
         | .........^, wantErr false
    --- FAIL: TestValidation/Homogeneous_Aggregate_Validation_test_6 (0.00s)