Forbid a single remaining tag to have a scrollbar

### What
This is a tiny styling issue, having the lowest priority possible, but nice to have at some point for improved look & feel.
(not reproducible with Electron Desktop Mac)

A single tag can have a scrollbar (2.9.0-beta1):

https://user-images.githubusercontent.com/73365754/112157402-d7dd9600-8bef-11eb-8701-f0441aed7534.mov

### Why
App will look better.

Start by reproducing the single-tag scrollbar shown in the linked video in the Simplenote app, noting that it was reported for version 2.9.0-beta1 and not reproduced on Electron Desktop Mac. Find the styling responsible for the tag display and verify that a single tag no longer shows an unwanted scrollbar.

Written by the indexing model from the issue text.