lodash: differenceBy/differenceWith update

[lukeapage]

• Links to documentation: https://lodash.com/docs/4.17.15#differenceBy
• Type of contribution: fix

Other notes:

when using differenceBy and differenceWith the types of the "values" and array do not need to match e.g.

_.differenceBy([{ id: 1, a: 2 }], [{ id: 1 }], ({ id }) => id);

In fact if using the by or with alternatives I would argue they are more likely to not match.

[valscion]

This seems to break the lodash tests. Would you be so kind to debug why the tests fail and maybe add a new test case to demonstrate why this change is needed?

[lukeapage]

@valscion the failures are on a part of the definition I didn't touch. I'm fairly sure its due to a new flow version that doesn't like part of the tests. I will try and send a pr to fix it and add a test to this one.

[lukeapage]

I merged the fix here but i suggest you merge #3714 first

[valscion]

Cool, thanks! This looks more ready to me now, and as the CI is green, this has a better chance of getting merged ☺️