wifi: rtlwifi: rtl8723: Remove unused function rtl8723_cmd_send_packet()

The function rtl8723_cmd_send_packet() is not used anywhere, so remove it.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230824062339.1885385-1-ruanjinjie@huawei.com