Filter: Neighborhoods/Community Org/Zone Pills: Unable to clear the pills using screen readers

## Description
Tracy Note: This ticket is related to https://github.com/CodeForPhilly/clean-and-green-philly/issues/631 & probably would be fixed with that refactor to pull out the selected pills from the dropdown.

Clearing the pills is impossible using NVDA & Voice Over. JAWS is more forgiving.

- NVDA + FF/Edge: Using tab key to navigate to the X button, selecting it activates the listbox pop up instead

Demo; see **from point 2:18** of the video onwards.

https://github.com/CodeForPhilly/clean-and-green-philly/assets/102739972/ade5b3b2-ca41-4165-ac9f-6bbbb8ca462c

- VO + Safari: Screen reader focus could not navigate to the pills at all; no feedback given when tabbing to it.

## Recommendation
- Would be better to not put the pill on top of the listbox popup so that there's a clear separation between the 2. It will also make the UI less confusing even for sighted users.

まず、Firefox/Edge では NVDA を、Safari では VoiceOver を使って filter-pill の動作を再現し、関連するリファクタリングのコンテキストとして issue 631 を使用します。完了条件は、スクリーンリーダーのユーザーが listbox を意図せずアクティブ化することなく、Neighborhoods、Community Org、Zone の pill に到達し、理解し、クリアできることです。

索引モデルが issue の本文から書いたものです。