Fixed out-of-bound access in CUDA Otsu threshold implementation.

[asmorkalov]

The issue introduced in #3943
Fixes #3962

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• I agree to contribute to the project under Apache 2 License.
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[asmorkalov]

cc @cudawarped

[cudawarped]

@cudawarped Nice catch I didn't notice @troelsy hadn't fixed everywhere! 🥳