Fix issue where connection was closed during retry.

- Resolved an issue where SnowflakeOutputConnection was prematurely closed during retries in the COPY operation.
- Refactored the code to use try-with-resources for managing SnowflakeOutputConnection, ensuring a new connection is created for each retry.
- Removed the explicit con.close() call in the finally block, as connections are now safely managed within the retry loop.

Author: kentoyoshida

src/main/java/org/embulk/output/snowflake/SnowflakeCopyBatchInsert.java

@@ -425,10 +425,10 @@ public Void call() throws SQLException, InterruptedException, ExecutionException
       try {
         uploadFuture.get();
 
-        SnowflakeOutputConnection con = (SnowflakeOutputConnection) connector.connect(true);
         int retries = 0;
         while (true) {
-          try {
+          try (SnowflakeOutputConnection con =
+              (SnowflakeOutputConnection) connector.connect(true)) {
             logger.info("Running COPY from file {}", snowflakeStageFileName);
 
             long startTime = System.currentTimeMillis();
@@ -461,8 +461,6 @@ public Void call() throws SQLException, InterruptedException, ExecutionException
                 String.format(
                     "Copy error %s file %s retries: %d", e, snowflakeStageFileName, retries));
             Thread.sleep(retries * retries * 1000);
-          } finally {
-            con.close();
           }
         }
       } finally {