[elm-client] Update dependency: elm-date-extra

Created by: andys8

Update dependency "justinmimbs/elm-date-extra": "2.0.0 <= v < 3.0.0".

There is a breaking change in the api.

The pattern matches things of type:

    Maybe a

But the values it will actually be trying to match are:

    Result String Date.Date

See

https://github.com/OpenAPITools/openapi-generator/blob/b5942624d6714f38c0bde9ae9c7400df1d48b1ed/modules/openapi-generator/src/main/resources/elm/DateTime.mustache

https://github.com/OpenAPITools/openapi-generator/blob/b5942624d6714f38c0bde9ae9c7400df1d48b1ed/modules/openapi-generator/src/main/resources/elm/elm-package.mustache#L15