Consistent UUID usage across file handling

src/main/java/com/drtshock/playervaults/vaultmanagement/UUIDVaultManager.java

@@ -186,8 +186,7 @@ public class UUIDVaultManager {
      * @throws IOException Uh oh!
      */
     public void deleteVault(CommandSender sender, UUID holder, int number) throws IOException {
-        String name = holder.toString();
-        File file = new File(directory, name.toLowerCase() + ".yml");
+        File file = new File(directory, holder.toString() + ".yml");
         if (!file.exists()) {
             return;
         }