Update TestValidation/Homogeneous_Aggregate_Validation_test_8

[polds]

TestValidation/Homogeneous_Aggregate_Validation_test_8 is broken. We should fix or remove.

=== RUN   TestValidation/Homogeneous_Aggregate_Validation_test_8
    eval_test.go:359: Compile() got error = a map key must be a quoted string, a number, a identifier, or an expression enclosed in parentheses (unexpected token Operator("?")) (1:18)
         | {'hello': false, ?'world': optional.ofNonZeroValue(true)}
         | .................^, wantErr false
    --- FAIL: TestValidation/Homogeneous_Aggregate_Validation_test_8 (0.00s)