Merge pull request #27589 from Kumataro:fix27588

imgcodecs: fix Imgcodecs_Png.write_big test for spng #27589

Close #27588 

### Pull Request Readiness Checklist

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- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/imgcodecs/test/test_png.cpp

@@ -20,7 +20,11 @@ TEST(Imgcodecs_Png, write_big)
 
     vector<uchar> buff;
     ASSERT_NO_THROW(imencode(".png", img, buff, { IMWRITE_PNG_ZLIBBUFFER_SIZE, INT_MAX }));
+#ifdef HAVE_PNG
     EXPECT_EQ((size_t)816219, buff.size());
+#else
+    EXPECT_EQ((size_t)817407, buff.size());
+#endif
 }
 
 TEST(Imgcodecs_Png, encode)