Doc: explain how to free allocated memory in SparseMAtrix
Doc: explain how to free allocated memory in SparseMAtrix

Zefz/eigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,toastedcrumpets/eigen,ROCmSoftwarePlatform/hipeigen,TSC21/Eigen,Zefz/eigen,toastedcrumpets/eigen,TSC21/Eigen,toastedcrumpets/eigen,ritsu1228/eigen,ritsu1228/eigen,ritsu1228/eigen,pasuka/eigen,TSC21/Eigen,ritsu1228/eigen,pasuka/eigen,ROCmSoftwarePlatform/hipeigen,TSC21/Eigen,pasuka/eigen,Zefz/eigen,ROCmSoftwarePlatform/hipeigen,toastedcrumpets/eigen,pasuka/eigen,Zefz/eigen