Grub Boot loader - removing the entry

Dear RHEL Community ,

Greetings! I am using RHEL 9 at home and I am Ubuntu user and new to RHEL. So, my desktop has triple OS booting system. (RHEL 9/ Ubuntu 22.04 / Windows 11).

At first, i have installed the RHEL along with Windows 11. Lately i have installed the Ubuntu. At moment, the Grub menu looks like (pls refer the screenshot) during boot. It is working with out any issue as long user the choose the correct entry / OS.
Question: How to remove the some of the kernel listing in Grub boot loader which is no longer used (RHEL_8.8) .I have tried the command

1. sudo grubby --info=ALL

2. grubby --remove-args="RHEL_8.8" --update-kernel /boot/vmlinuz-4.18.0-477.15.1.el8_8.x86_64

But it not working i.e the old kernel is not removed. Do you need to update the Grub after first 2 commands? Am i missing anything? Please advise