R1:e5a16819031e

Render timezone names more readably, with spaces rather than underscores ("America/Los Angeles", not "America/Los_Angeles").

Summary:
See downstream <https://phabricator.wikimedia.org/T902>. Currently, timezones are rendered with their raw internal names (like `America/Los_Angeles`) which include underscores.

Replacing underscores with spaces is a more human-readable (and perhaps meaningfully better for things like screen readers, although this is pure speculation).

There's some vague argument against…