locatedError: correct definition to pass Flow 0.68 check

[IvanGoncharov]

Not sure how to fix other $FlowFixMe introduced in #1291 but this was a low hanging fruit.

[leebyron]

Seems weird. GraphQLError should be a subset of Error, so not required to explicitly declare. I'll take a look

[IvanGoncharov]

Seems weird. GraphQLError should be a subset of Error, so not required to explicitly declare. I'll take a look

@leebyron It's happening because of this change in Flow:

Likely to cause new Flow errors:

Previously, Flow would allow you to write if (foo.unknownProp) { ... }.

Now Flow disallows testing unknown properties in conditionals. If foo is a
union type like { x: string } | { y: number }, x and y are known
properties and z would be an unknown property

So after this change, you can't test if an instance of Error has path property.
But the same check works for instances of GraphQLError.

[leebyron]

Ahhh, yes that makes sense. Thanks for the explanation!