Revert "Re-enable (most) iOS Scenarios tests"

This reverts flutter#21087, which speculatively re-enabled the Scenarios iOS
tests once we'd got Dart/Skia/Fuchsia rolls in, which had been blocked
by flaky test runs. We'd hoped that that PR would be sufficient to
eliminate the tree closures but new tests within the suite started
failing instead. Reverting while the issue is root-caused and fixed.

Related P0 issue: flutter/flutter#61620

This reverts commit bdaac36.

Author: cbracken

testing/scenario_app/run_ios_tests.sh

@@ -33,9 +33,14 @@ if [[ $# -eq 1 ]]; then
   FLUTTER_ENGINE="$1"
 fi
 
-cd ios/Scenarios
-set -o pipefail && xcodebuild -sdk iphonesimulator \
-  -scheme Scenarios \
-  -destination 'platform=iOS Simulator,name=iPhone 8' \
-  test \
-  FLUTTER_ENGINE="$FLUTTER_ENGINE"
+echo "iOS Scenarios tests currently disabled due to flakiness"
+echo "See: https://github.com/flutter/flutter/issues/61620"
+
+# TODO(cbracken): re-enable when
+# https://github.com/flutter/flutter/issues/61620 is fixed.
+# cd ios/Scenarios
+# set -o pipefail && xcodebuild -sdk iphonesimulator \
+#   -scheme Scenarios \
+#   -destination 'platform=iOS Simulator,name=iPhone 8' \
+#   test \
+#   FLUTTER_ENGINE="$FLUTTER_ENGINE"