fix: close HttpClient after binlog download to prevent resource leak (#5579)

BinlogDownloadQueue.download() creates a CloseableHttpClient for each
download but never closes it. Over time this exhausts connection pool
resources. Wrap the HTTP execution in a try-finally block to ensure the
client is always closed.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

parse/src/main/java/com/alibaba/otter/canal/parse/inbound/mysql/rds/BinlogDownloadQueue.java

@@ -189,6 +189,7 @@ public class BinlogDownloadQueue {
             httpClient = HttpClientBuilder.create().setMaxConnPerRoute(50).setMaxConnTotal(100).build();
         }
 
+        try {
             HttpGet httpGet = new HttpGet(downloadLink);
             RequestConfig requestConfig = RequestConfig.custom()
                 .setConnectTimeout(TIMEOUT)
@@ -202,6 +203,9 @@ public class BinlogDownloadQueue {
                 throw new RuntimeException("download failed , url:" + downloadLink + " , statusCode:" + statusCode);
             }
             saveFile(new File(destDir), "mysql-bin." + fileName, response);
+        } finally {
+            httpClient.close();
+        }
     }
 
     private static void saveFile(File parentFile, String fileName, HttpResponse response) throws IOException {