Build warning fix on Windows.

[asmorkalov]

Address CI warning:

c:\build\precommit_windows64\4.x\opencv_contrib\modules\wechat_qrcode\src\zxing\common\../zxing.hpp(58): warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning) [C:\build\precommit_windows64\build\modules\wechat_qrcode\opencv_wechat_qrcode.vcxproj]
c:\build\precommit_windows64\4.x\opencv_contrib\modules\wechat_qrcode\src\zxing\common\../zxing.hpp(59): warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning) [C:\build\precommit_windows64\build\modules\wechat_qrcode\opencv_wechat_qrcode.vcxproj]

Introduced in #3490

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• 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
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• 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