Fixes fluky Java tests behavior on Windows CI.
The original code used C-style string. The C string finishes at zero symbol. Byte array does not have zero symbol at the end and Java wrapper just adds random piece of garbage (till zero byte in memory) at the sequence end.

Pull Request Readiness Checklist

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• I agree to contribute to the project under Apache 2 License.
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  Patch to opencv_extra has the same branch name.
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