Updated nicegui methods for js libraries requires updates

[carlhiggs]

Describe the bug
The implementation of external javascript libraries seems to have changed in nicegui, and so the latest Docker image (4.4.8) that uses the newer version requires some changes (e.g. in order for our Leaflet implementation to work).

To Reproduce
On enhancements using image 4.4.8 and this portion of the current Leaflet.py code,

https://github.com/global-healthy-liveable-cities/global-indicators/blob/2ba788e601ebecbf374025986c69f9ac0ad9ea0e/process/subprocesses/leaflet.py#L3-L16

results in this error when attempting to launch the ghsci process:

# ghsci
Traceback (most recent call last):
  File "/home/ghsci/process/gui.py", line 18, in <module>
    from subprocesses.leaflet import leaflet
  File "/home/ghsci/process/subprocesses/leaflet.py", line 6, in <module>
    from nicegui.dependencies import register_component
ImportError: cannot import name 'register_component' from 'nicegui.dependencies' (/env/lib/python3.10/site-packages/nicegui/dependencies.py)

This relates to changes in nicegui, as per their Leaflet map example that I based this code on:
zauberzeug/nicegui@4c5745b

So -- we just need to update to use the updated syntax