Restrict optype to <0.18 #856

Job	Run time
Python 3 Examples	1m 4s
Ruff	6s
basedpyright	3s
Documentation	1m 10s
Tests for downstream project pytential	1m 9s
Typos	4s
Conda Python 3	1m 11s
Tests for downstream project sumpy	1m 8s
	5m 55s

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