refactor(proxy): 优化日志信息内容

- 将 cert file changed 日志信息改为更通用的 File changed
- 保持代码风格一致性，提高日志的可读性和维护性

Signed-off-by: Async <raisinata@foxmail.com>

Author: EnableAsync

proxy/src/main/java/org/apache/rocketmq/proxy/service/cert/TlsCertificateManager.java

@@ -80,7 +80,7 @@ private class CertKeyFileWatchListener implements FileWatchService.Listener {
 
         @Override
         public void onChanged(String path) {
-            log.info("cert file changed: {}", path);
+            log.info("File changed: {}", path);
             if (path.equals(TlsSystemConfig.tlsServerCertPath)) {
                 certChanged = true;
             } else if (path.equals(TlsSystemConfig.tlsServerKeyPath)) {