Remove fuchsia tests from sdk recipe.

Fuchsia tests will get added to their own recipe so they don't need to
affect the other sdk tests.

Change-Id: I86f2421fbbbc32369197d275b65a21daa0f082b6
Bug: https://github.com/flutter/flutter/issues/57044
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/2826
Reviewed-by: Kaushik Iska <kaushikiska@google.com>