remove reliance on remote datasets in tests

[jameslamb]

Description

One test here downloads a file from a non-RAPIDS repo (https://github.com/loganpowell/census-geojson) on every run:

cuxfilter/python/cuxfilter/tests/charts/deckgl/test_deckgl.py

Lines 20 to 34 in 6237ba1

	choropleth3d_chart = charts.choropleth(
	x="states",
	color_column="val",
	elevation_column="val_t",
	color_aggregate_fn="mean",
	elevation_aggregate_fn="count",
	add_interaction=False,
	elevation_factor=100000,
	geoJSONSource=(
	"https://raw.githubusercontent.com/loganpowell/census-geojson"
	"/master/GeoJSON/5m/2018/state.json"
	),
	geoJSONProperty="STATEFP",
	map_style="testMap",
	)

That should be factored out.

Benefits of this work

• improves CI stability (ref: Build and test with CUDA 12.8.0 #649 (review))
• reduces the risk of disruption for developers running tests locally (especially in environments with weak internet connection)

Acceptance Criteria

• tests do not depend on downloading external data (where avoidable)

Approach

Some possible alternatives:

• using synthetic geojson data generated at test time
• using test data checked into source control here (ideally a smaller file, if appropriate... that file is 2.1MB)
• removing the test (if on a re-review, it seems to not be useful)

Notes

N/A