Filter zero division examples for test_remainder

[honno]

For integers, zero division is out-of-scope. cc @pmeier

[honno]

There's another bug with the not_nan mask I see, must of been there for awhile. It also didn't check if the out array had a float dtype. Generally I think more can be done to test the output of remainder (I guess this was left alone as remainder behaviour was ambiguous at the time), but for now I'll leave it all out so at least we have a working smoke test.