fix(odc-desktop): download size of datasource_template always is 0B (#4471)

* add code

* change

Author: ysjemmm

server/odc-service/src/main/java/com/oceanbase/odc/service/connection/ConnectionService.java

@@ -893,8 +893,7 @@ public BinaryDataResult getBatchImportTemplateFile() throws IOException {
             if (input == null) {
                 throw new UnexpectedException(DATASOURCE_TEMPLATE_FILE_NAME + " is not found");
             }
-            byte[] buffer = new byte[input.available()];
-            IOUtils.read(input, buffer);
+            byte[] buffer = IOUtils.toByteArray(input);
             return new ByteArrayDataResult(DATASOURCE_TEMPLATE_FILE_NAME, buffer);
         }
     }