[fuchsia_modular_testing] Fix strict dependencies

Unused/undeclared deps break the build if it has Dart strict deps enabled.

Bug: b/149930618
Change-Id: If853e27296d509ca1b5845c3bd7731ab76111466
diff --git a/public/dart/fuchsia_modular_testing/BUILD.gn b/public/dart/fuchsia_modular_testing/BUILD.gn
index d424a24..3d559a6 100644
--- a/public/dart/fuchsia_modular_testing/BUILD.gn
+++ b/public/dart/fuchsia_modular_testing/BUILD.gn
@@ -27,7 +27,7 @@
     "//sdk/fidl/fuchsia.modular.session",
     "//sdk/fidl/fuchsia.modular.testing",
     "//sdk/fidl/fuchsia.sys",
-    "//sdk/fidl/fuchsia.ui.app",
+    "//third_party/dart-pkg/pub/meta",
     "//topaz/public/dart/fidl",
     "//topaz/public/dart/fuchsia_logger",
     "//topaz/public/dart/fuchsia_modular",