Incorrect timezone offset displayed in World Clocks under certain conditions

[bitinerant]

I have observed this bug in Ubuntu 22.04 and Ubuntu 24.04.

To reproduce:
* Set the system time to a timezone that does not have DST, e.g. `sudo timedatectl set-timezone Africa/Tunis`
* Add at least one timezone to the Gnome World Clocks that does have DST, e.g. London or Paris.
* Wait for DST to change in the other timezone.
* Note the incorrect 'timezone offset' column for the remote timezone(s) (circled in red in the left-hand screenshot). Interestingly, the 'time' column is correct for every timezone.
* Change the system timezone and then change it back, e.g. `sudo timedatectl set-timezone America/Los_Angeles && sudo timedatectl set-timezone Africa/Tunis` --OR-- reboot.
* Note the 'timezone offset' column is correct now (the right-hand screenshot).

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: gnome-shell 46.0-0ubuntu6~24.04.5
ProcVersionSignature: Ubuntu 6.8.0-47.47-generic 6.8.12
Uname: Linux 6.8.0-47-generic x86_64
NonfreeKernelModules: zfs
ApportVersion: 2.28.1-0ubuntu3.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Mon Oct 28 19:55:11 2024
DisplayManager: gdm3
InstallationDate: Installed on 2024-06-08 (142 days ago)
InstallationMedia: Ubuntu 24.04 LTS "Noble Numbat" - Release amd64 (20240424)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
RelatedPackageVersions: mutter-common 46.2-1ubuntu0.24.04.2
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)