Use Java 21 to compile/build

Author: chadlwilson

jitpack.yml

@@ -1,10 +1,10 @@
 jdk:
-  - openjdk17
+  - openjdk21
 
 before_install:
   - source "$HOME/.sdkman/bin/sdkman-init.sh"
   - sdk update
   - sdk install maven
-  - sdk install java 17.0.14.7-tem
-  - sdk use java 17.0.14.7-tem
-  - mvn -v
+  - sdk install java 21.0.7.6-tem
+  - sdk use java 21.0.7.6-tem
+  - mvn -v