update zh-cn/application-dev/reference/apis/js-apis-file-statvfs.md.

Signed-off-by: Nzengyawen <zengyawen1@huawei.com>

zh-cn/application-dev/reference/apis/js-apis-file-statvfs.md

@@ -42,7 +42,7 @@ getFreeSize(path:string):Promise<number>
   });
   ```
 
-## statfs.getFreeSize
+## statvfs.getFreeSize
 
 getFreeSize(path:string, callback:AsyncCallback<number>): void
 
@@ -70,7 +70,7 @@ getFreeSize(path:string, callback:AsyncCallback<number>): void
   });
   ```
 
-## statfs.getTotalSize
+## statvfs.getTotalSize
 
 getTotalSize(path: string): Promise<number>
 
@@ -101,7 +101,7 @@ getTotalSize(path: string): Promise<number>
   });
   ```
 
-## statfs.getTotalSize
+## statvfs.getTotalSize
 
 getTotalSize(path: string, callback: AsyncCallback<number>): void