Update s3-java to use java21

Author: AWSBen

sample-apps/s3-java/README.md

@@ -14,7 +14,7 @@ The project source includes function code and supporting resources:
 Use the following instructions to deploy the sample application.
 
 # Requirements
-- [Java 8 runtime environment (SE JRE)](https://www.oracle.com/java/technologies/javase-downloads.html)
+- [Java 21 runtime environment (SE JRE)](https://www.oracle.com/java/technologies/javase-downloads.html)
 - [Gradle 5](https://gradle.org/releases/) or [Maven 3](https://maven.apache.org/docs/history.html)
 - The Bash shell. For Linux and macOS, this is included by default. In Windows 10, you can install the [Windows Subsystem for Linux](https://docs.microsoft.com/en-us/windows/wsl/install-win10) to get a Windows-integrated version of Ubuntu and Bash.
 - [The AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-install.html) v1.17 or newer.

sample-apps/s3-java/template.yml

@@ -10,7 +10,7 @@ Resources:
     Properties:
       CodeUri: build/distributions/s3-java.zip
       Handler: example.Handler
-      Runtime: java8
+      Runtime: java21
       Description: Java function
       MemorySize: 512
       Timeout: 30
@@ -42,4 +42,4 @@ Resources:
       Description: Dependencies for the Java S3 sample app.
       ContentUri: build/s3-java-lib.zip
       CompatibleRuntimes:
-        - java8
+        - java21