Disable iOS ScenariosTests suite (#21080)

This disables the macOS Scenarios app tests until a fix for the current
flakiness is found.

This also reverts commit 55d447a1 where
one test was previously disabled. However, another started failing soon
after, so instead we disable the whole suite here.

testing/scenario_app/ios/Scenarios/ScenariosTests/AppLifecycleTests.m

@@ -227,9 +227,7 @@ FLUTTER_ASSERT_ARC
   [engine setViewController:nil];
 }
 
-// TODO(cbracken): re-enable this test by removing the skip_ prefix once the source of its flakiness
-// has been identified. https://github.com/flutter/flutter/issues/61620
-- (void)skip_testFlutterViewControllerDetachingSendsApplicationLifecycle {
+- (void)testFlutterViewControllerDetachingSendsApplicationLifecycle {
   XCTestExpectation* engineStartedExpectation = [self expectationWithDescription:@"Engine started"];
 
   // Let the engine finish booting (at the end of which the channels are properly set-up) before

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"