test_vecdot does not test for conjugation in the first parameter

It looks like there isn't any values testing in test_vecdot at all for floating-point arguments. We should add something so that the conjugation can be tested, since this is something many implementations miss (e.g., https://github.com/data-apis/array-api-compat/issues/200, https://github.com/data-apis/array-api-strict/issues/97). 