improve WebbPSF data caching in GitHub CI #2701

Job	Run time
data / fetch, check, and possibly update webbpsf data cache	13s
check / Load tox environments	13s
data / retrieve current CRDS context, and WebbPSF data	4s
check / check-dependencies (ubuntu-latest)	2m 17s
check / build-dist (ubuntu-latest)	29s
test / Load tox environments	5s
test / py39-oldestdeps-cov (ubuntu-latest)	9m 10s
test / py39 (ubuntu-latest)	10m 23s
test / py310 (ubuntu-latest)	6m 32s
test / py311-ddtrace (ubuntu-latest)	7m 54s
test / py311-ddtrace (macos-latest)	10m 36s
test / py311-cov (ubuntu-latest)	12m 9s
	1h 0m 5s

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