Clarify the optional Anaconda installation step in docs #7931

Job	Run time
mypy	1m 43s
docs	3m 50s
lint	4s
arkouda_benchmark_linux (chapel, 2)	8m 59s
arkouda_chpl_portability (2.0.0)	1h 28m 2s
arkouda_multi-dim (2.0.0)	20m 26s
arkouda_python_portability (3.9)	13m 17s
flake8	1m 28s
arkouda_python_portability (3.10)	14m 7s
arkouda_tests_linux (chapel, 2)	15m 2s
arkouda_python_portability (3.11)	13m 23s
	3h 0m 21s

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