Update TestValidation/Timestamp_Validation_test_3

TestValidation/Timestamp_Validation_test_3 is broken. We should fix or remove.

```
=== RUN   TestValidation/Timestamp_Validation_test_3
    eval_test.go:349: Compile() got error = unknown name timestamp (1:1)
         | timestamp('1000-01-01T00:00:00Z')
         | ^, wantErr false
    --- FAIL: TestValidation/Timestamp_Validation_test_3 (0.00s)
```