Fix examples for JDK 21 (Android Studio Ladybug) #1912

Job	Run time
flutter-integration-test (macos-13, 3.24.2)	13m 53s
flutter-integration-test (macos-13, 3.16.9)	11m 21s
generator	5m 23s
flutter-integration-test (ubuntu-24.04, 3.24.2)	9m 32s
init-script	3m 21s
flutter-integration-test (ubuntu-24.04, 3.16.9)	8m 12s
flutter-integration-test (windows-2022, 3.24.2)	7m 39s
lib (windows-2022, 3.5.2)	1m 53s
lib (windows-2022, 3.4.4)	1m 56s
flutter-integration-test (windows-2022, 3.16.9)	8m 29s
lib (windows-2022, 2.18.6)	2m 5s
lib (macos-13, 3.5.2)	1m 58s
lib (macos-13, 3.4.4)	2m 53s
lib (macos-13, 2.18.6)	3m 32s
lib (ubuntu-24.04, 3.5.2)	1m 31s
lib (ubuntu-24.04, 3.4.4)	1m 23s
lib (ubuntu-24.04, 2.18.6)	1m 38s
	1h 26m 39s

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