delete incorrectly applied on some allocations from new[]

[david-cortes]

From #4982

The function LGBM_BoosterFreePredictSparse uses C++ operator delete to free outputs passed from the C side:

LightGBM/src/c_api.cpp

Line 1969 in 0075814

delete reinterpret_cast<int32_t*>(indptr);

These outputs are allocated with operator new[]:

LightGBM/src/c_api.cpp

Line 599 in 0075814

*out_col_ptr = new int32_t[col_ptr_size];

Thus, it needs to use delete[], not delete, otherwise it can lead to crashes and undefined behavior.

[github-actions]

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