Switch to ryan-haskell/date-format to fix storybook build.

[xaviershay]

A similar change has already been applied to the main elm.json file, and I also found similar changes in other (unrelated) codebases. Copying the version range from base elm.json didn't work (difference between libs in dependences vs dependencies/direct?), so pinned to an exact version instead.

I have no Elm experience, there may be a better way to solve this.

[yoching]

Which part of the storybook was broken? In my environment, it seems that both storybook dev and storybook build are working.

[hojberg]

IIRC, this is the same library and author, but Ryan changed their username to ryan-haskell, which we should probably use going forward.