fix(upload_image): 优化临时文件删除逻辑及提示文本显示

- 仅在jpg文件类型时删除临时文件，防止误删其他文件类型
- 修正上传图片提示中相册最大数量变量显示问题，提升用户体验

lib/upload_image/ossUtil.dart

@@ -77,8 +77,10 @@ class UploadOss {
       );
       print("response ===== $response");
       EasyLoading.dismiss();
+      if(fileType == 'jpg'){
         /// 删除临时文件
         File(path).deleteSync();
+      }
       // 成功后返回文件访问路径
       return "$ossHost/$ossDirectory$pathName";
     } on DioError catch (e) {

lib/upload_image/upload_image.dart

@@ -280,7 +280,7 @@ class _UploadImagesState extends State<UploadImages> {
             title: const Text('上传图片'),
             message: (max == null || max == 0)
                 ? null
-                : Text('请选择上传方式\n相册最多${max ?? 9}张'),
+                : Text('请选择上传方式\n相册最多$max张'),
             actions: <Widget>[
               CupertinoActionSheetAction(
                 child: const Text('拍照上传'),