update pytz dependency

[chrisdicaprio]

pytz is pinned to 2021.3, propose updating pytz dependency to ^2025.1 to make use of solvis with other packages easeir. For example when attempting to add solvis to runzi:

hrisdc@hutl24256:~/.../APP/nzshm-runzi (182-disagg)$ poetry add git+https://github.com/GNS-Science/solvis.git#pre-release

Updating dependencies
Resolving dependencies... (0.0s)

Because solvis (0.13.0) @ git+https://github.com/GNS-Science/solvis.git@pre-release depends on pytz (2021.3)
 and nzshm-runzi depends on pytz (^2022.7), solvis is forbidden.
So, because nzshm-runzi depends on solvis (0.13.0) @ git+https://github.com/GNS-Science/solvis.git@pre-release, version solving failed.