Change ryannhg/date-format to ryan-haskell/date-format

The build was failing because the GitHub user changed their username:
https://discourse.elm-lang.org/t/ryannhg-packages-renamed-to-ryan-haskell/9705

Confusingly, 1.0.0 is the latest (and only) version in the registry:
(https://package.elm-lang.org/packages/ryan-haskell/date-format/latest/.
The GitHub repo has 2.3.0 tagged on a much older commit.

Change-Id: Ib3b20e65a7d39cd3df8f8ffe76d4d66cbd644b51
Reviewed-on: https://fuchsia-review.googlesource.com/c/fidlbolt/+/1035992
Reviewed-by: Clayton Wilkinson <wilkinsonclay@google.com>
diff --git a/frontend/src/elm/elm.json b/frontend/src/elm/elm.json
index 7c70723..0848153 100644
--- a/frontend/src/elm/elm.json
+++ b/frontend/src/elm/elm.json
@@ -12,7 +12,7 @@
             "elm/json": "1.1.3",
             "elm/regex": "1.0.0",
             "elm/time": "1.0.0",
-            "ryannhg/date-format": "2.3.0"
+            "ryan-haskell/date-format": "1.0.0"
         },
         "indirect": {
             "elm/url": "1.0.0",