Modify the use case of decodeWithStream interface xts in TextDecoder class under util

Signed-off-by: N@wang-jingwu001 <wangjingwu3@huawei.com>
https://gitee.com/openharmony/xts_acts/issues/I5N2R8

commonlibrary/ets_utils/util_lib_standard/src/main/js/test/util.test.js

@@ -902,7 +902,7 @@ describe('TextEncoderTest', function () {
         var BOM = '\uFEFF';
         var rel = 'abc';
         var re = BOM + rel;
-        expect(retStr).assertEqual(rel)
+        expect(retStr).assertEqual(re)
     })
 
     /**
@@ -923,7 +923,7 @@ describe('TextEncoderTest', function () {
         var BOM = '\uFEFF'
         var rel = 'abc'
         var re = BOM + rel;
-        expect(retStr).assertEqual(rel)
+        expect(retStr).assertEqual(re)
     })
 
     /**