chore:upgrade java8 to java21 for appidentity folder#10151

Alesvoy wants to merge 2 commits intoGoogleCloudPlatform:mainGoogleCloudPlatform/java-docs-samples:mainfrom

Alesvoy:abutron-chore-migrate-java8-to-java21-appidentityAlesvoy/java-docs-samples:abutron-chore-migrate-java8-to-java21-appidentityCopy head branch name to clipboard