Investage translation with str_replace in TimeZoneFormHelper.php

Problem/Motivation

Investigate this code in TimeZoneFormHelper.php and either add a comment about why this is correct or do something different.

foreach ($zone_list as $zone) {$zones[$zone] = new TranslatableMarkup(str_replace('_', ' ', $zone));

Follow up from #3123067: Fix 'Drupal.Semantics.FunctionT.NotLiteralString' coding standard →

Steps to reproduce

Proposed resolution

TBD

Remaining tasks

Investigate and decide on a course of action
Update issue title based on the decision
Review

User interface changes

API changes

Data model changes

Release notes snippet