Bump gradle in /examples/fabric-contract-example-as-service

Bumps gradle from 8-jdk21 to 9-jdk21.

---
updated-dependencies:
- dependency-name: gradle
  dependency-version: 9-jdk21
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

examples/fabric-contract-example-as-service/Dockerfile

@@ -4,7 +4,7 @@
 # Example multi-stage dockerfile for Java Chaincode
 
 # the first stage 
-FROM gradle:8-jdk21 AS gradle_build
+FROM gradle:9-jdk21 AS gradle_build
 
 # copy the build.gradle and src code to the container
 COPY src/ src/