fix: fill match arms on last comma and empty expr

[A4-Tacks]

For Vim, triggering code action at the end of line usually occurs before the last character rather than after it

Example

fn foo() {
    match Some(2) {
        Some(_) => ()$0,
    }
}

Before this PR

Assist not applicable

After this PR

fn foo() {
    match Some(2) {
        Some(_) => (),
        None => ${1:todo!()},$0
    }
}