Fix brace_style="PreferSameLine" with trailing_comma="Vertical" results

[gentoid]

Fixes #2321

• Fixed trailing comma did not disappear when configured brace_style="PreferSameLine" and trailing_comma="Vertical".
• Fixed test case.

Example

When brace_style="PreferSameLine" and trailing_comma="Vertical" configured, the results would be as in the following example:

before

fn lorem<S, T>(lorem: S, ipsum: T)
where
    S: Add + Sub,
    T: Mul + Div, { // ← trailing comma is not removed from the bound
    // body
}

after

fn lorem<S, T>(lorem: S, ipsum: T)
where
    S: Add + Sub,
    T: Mul + Div {
    // body
}

NOTE

This is continuation of a PR #5556, which seems to be abandoned. All the credits go to @hirasawayuki . I'll adjust the code if need be. For now, I only synched the branch with master.

[calebcartwright]

Thanks for the PR!

@ytmimi I know you've a lot on your plate already, but was wondering if you'd want to review this one given you were pretty engaged with it back on #5556