fixed 2b595918 from https://gitee.com/zengyawen/docs/pulls/14464

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

@@ -35,7 +35,7 @@ getFreeSize(path:string):Promise<number>
 
   ```js
   let path = "/dev";
-  statfs.getFreeSize(path).then((number) => {
+  statvfs.getFreeSize(path).then((number) => {
     console.info("getFreeSize promise successfully, Size: " + number);
   }).catch((err) => {
     console.info("getFreeSize failed with error message: " + err.message + ", error code: " + err.code);
@@ -61,7 +61,7 @@ getFreeSize(path:string, callback:AsyncCallback<number>): void
 
   ```js
   let path = "/dev";
-  statfs.getFreeSize(path, (err, number) => {
+  statvfs.getFreeSize(path, (err, number) => {
     if (err) {
       console.info("getFreeSize failed with error message: " + err.message + ", error code: " + err.code);
     } else {
@@ -94,7 +94,7 @@ getTotalSize(path: string): Promise<number>
 
   ```js
   let path = "/dev";
-  statfs.getTotalSize(path).then((number) => {
+  statvfs.getTotalSize(path).then((number) => {
     console.info("getTotalSize promise successfully, Size: " + number);
   }).catch((err) => {
     console.info("getTotalSize with error message: " + err.message + ", error code: " + err.code);
@@ -120,7 +120,7 @@ getTotalSize(path: string, callback: AsyncCallback<number>): void
 
   ```js
   let path = "/dev";
-  statfs.getTotalSize(path, (err, number) => {
+  statvfs.getTotalSize(path, (err, number) => {
     if (err) {
       console.info("getTotalSize with error message: " + err.message + ", error code: " + err.code);
     } else {