Update TestValidation/Regex_Validation_test_5

 TestValidation/Regex_Validation_test_5 is broken. We should fix or remove.

```
=== RUN   TestValidation/Regex_Validation_test_5
    eval_test.go:349: Compile() got error = unexpected token Operator(".") (1:8)
         | 'hello'.matches(x)
         | .......^, wantErr false
    --- FAIL: TestValidation/Regex_Validation_test_5 (0.00s)
```