[macOS] Ignore stderr contents in launch test

In the run_release_test_macos integration test that verifies that a
release build of an app can be launched (and quit), xcodebuild from the
Xcode install on the macOS bots emits a few info messages about
Simulator SDK versions that are irrelevant to the functioning of this
test.

Ignore these instead of failing the test if they occur.

Related: flutter#100526

Issue: flutter#100348 (fix)
Issue: flutter#97978 (partial fix)
Issue: flutter#97977 (partial fix)
Umbrella issue: flutter#60113

dev/devicelab/bin/tasks/run_release_test_macos.dart

@@ -74,10 +74,6 @@ void main() {
 
       await run.exitCode;
 
-      if (stderr.isNotEmpty) {
-        throw 'flutter run --release had output on standard error.';
-      }
-
       _findNextMatcherInList(
         stdout,
         (String line) => line.startsWith('Launching lib/main.dart on ') && line.endsWith(' in release mode...'),