Sidious has no more use for Jar Jar, he will enslave him or kill him. But giving Jar Jar screen time just to see him die?
It wouldn't fit in the movie, it would be a useless scene and it would ruin the entire ending of the movie because some people wanted Jar Jar to die.
They could have added something in the funeral scene were Padmé goes down in a tomb Jar Jar follows and then the door just closes. I wouldn't have cared about that, but adding an entire scene just to see him die? No way in hell.