Update installation instructions for spicepy@v3.0.0 #340

Job	Run time
Test with pip install 3.12	18s
Test with pip install 3.11	16s
Test on ubuntu-latest with pytest 3.12	1m 9s
Test on ubuntu-latest with pytest 3.11	1m 9s
Test on macos-latest with pytest 3.12	38s
Test on macos-latest with pytest 3.11	30s
Test on windows-latest with pytest 3.12	2m 36s
Test on windows-latest with pytest 3.11	2m 21s
	8m 57s

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