Fix exception message

Co-authored-by: Abhisar Sinha <63767682+abh1sar@users.noreply.github.com>

Author: Damans227

server/src/main/java/org/apache/cloudstack/backup/BackupManagerImpl.java

@@ -1560,7 +1560,7 @@ private void checkForPendingBackupJobs(final BackupVO backup) {
                 CreateVMFromBackupCmdByAdmin.class.getName(),
                 RestoreBackupCmd.class.getName());
         if (pendingJobs > 0) {
-            throw new CloudRuntimeException("Cannot delete backup while a create instance from backup or restore operation is in progress, please try again later.");
+            throw new CloudRuntimeException("Cannot delete Backup while a create Instance from Backup or restore Backup operation is in progress, please try again later.");
         }
     }