Bump dtoolcore from 3.18.2 to 3.18.3 #557

Job	Run time
publish-on-pypi	2m 4s
build-on-windows / build	2m 26s
build-installer-on-windows / build	2m 23s
build-on-macos / build	1s
build-on-ubuntu / build	3m 14s
publish-on-github	0s
	10m 8s

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