Update mkdocs.yml (#14)

mkdocs.yml

@@ -527,13 +527,13 @@ nav:
           - OpenLDAP 验证: 7.data-security/1.authentication/4.ldap.md
       - SSL 加密: 7.data-security/4.ssl.md
 
- - 备份与恢复:
-     - 悦数备份&恢复:
-       - 悦数备份&恢复概述: backup-and-restore/1.br-ent-overview.md
-       - 安装: backup-and-restore/2.install-tools.md
-       - 备份数据: backup-and-restore/3.backup-data.md
-       - 恢复数据: backup-and-restore/4.restore-data.md
-     - 快照: backup-and-restore/3.manage-snapshot.md
+  - 备份与恢复:
+      - 悦数备份&恢复:
+        - 悦数备份&恢复概述: backup-and-restore/1.br-ent-overview.md
+        - 安装: backup-and-restore/2.install-tools.md
+        - 备份数据: backup-and-restore/3.backup-data.md
+        - 恢复数据: backup-and-restore/4.restore-data.md
+      - 快照: backup-and-restore/3.manage-snapshot.md
 
   - 同步与迁移:
       - 负载均衡: synchronization-and-migration/2.balance-syntax.md