Fix Unused Variable Warning in test_rotation_and_scale_invariance.cpp

[shyama7004]

Description:

This PR resolves a warning caused by an unused variable IMAGE_BIKES in the file test_rotation_and_scale_invariance.cpp within the xfeatures2d module of the OpenCV contrib repository.

• Issue: The variable IMAGE_BIKES was declared but not used in the test file, leading to a compiler warning (-Wunused-const-variable).

warning: unused variable 'IMAGE_BIKES' [-Wunused-const-variable]
static const char* const IMAGE_BIKES = "detectors_descriptors_evaluation/

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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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