Fix trailing whitespace

08_data/8.1_volume.md

@@ -37,7 +37,7 @@ graph TD
         Image[镜像层<br>ReadOnly]
         Writable --- Image
     end
-    
+
     Lifecycle[生命周期 = 容器生命周期] -.-> Container
     Delete[容器删除] -->|导致| DataLost[数据丢失 ❌]
 ```
@@ -49,11 +49,11 @@ graph TD
     subgraph Container [容器]
         AppDir["/app/data"]
     end
-    
+
     subgraph Volume [数据卷 my-data]
         Data[持久化数据]
     end
-    
+
     AppDir == 挂载 ==> Volume
     Delete[容器删除] -.->|不会影响| Volume
 ```