Update Nightly Cleanup to Java21 (#2938)

Author: MohananRahul

JenkinsJobs/Cleanup/pruneDailyRepos.groovy

@@ -12,6 +12,7 @@ and other such scripts.
     numToKeep(5)
   }
 
+ jdk('temurin-jdk21-latest')
 
   label('basic')
 

cje-production/cleaners/cleanupNightlyRepo.sh

@@ -159,7 +159,7 @@ function cleanRepo ()
     echo -e "\t${eclipseexe}"
     exit 1
   fi
-  javaexe=/opt/public/common/java/openjdk/jdk-17_x64-latest/bin/java
+  javaexe=${JAVA_HOME}/bin/java
   if [[ ! -x ${javaexe} ]]
   then
     echo -e "\n\tERROR: expected java location not found, or not executable"