update pyabacus contributing md

Author: Cstandardlib

python/pyabacus/CONTRIBUTING.md

@@ -189,7 +189,7 @@ list(APPEND _diago
     ${HSOLVER_PATH}/diago_david.cpp
     ${HSOLVER_PATH}/diag_const_nums.cpp
     ${HSOLVER_PATH}/diago_iter_assist.cpp
-    ${HSOLVER_PATH}/kernels/dngvd_op.cpp
+    ${HSOLVER_PATH}/kernels/hegvd_op.cpp
     ${HSOLVER_PATH}/kernels/bpcg_kernel_op.cpp
     ${BASE_PATH}/kernels/math_kernel_op.cpp
     ${BASE_PATH}/kernels/math_kernel_op_vec.cpp