Update to Java 21

Change-Id: I68d241c6a1d8da97f212647a3da2ac3793fe4f72
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 45dff3a..68208fb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,4 +1,4 @@
-image: maven:3-eclipse-temurin-17-alpine
+image: maven:3-eclipse-temurin-21-alpine
 
 stages:
     - build