Disallow used supply/resource item deletion #6

Job	Run time
redmine:4.2-stable ruby:2.7 db:postgres	1m 37s
redmine:4.2-stable ruby:2.7 db:sqlite	1m 32s
redmine:5.0-stable ruby:2.7 db:postgres	1m 55s
redmine:5.0-stable ruby:2.7 db:sqlite	1m 38s
redmine:5.0-stable ruby:3.0 db:postgres	1m 37s
redmine:5.0-stable ruby:3.0 db:sqlite	1m 37s
redmine:5.0-stable ruby:3.1 db:postgres	1m 35s
redmine:5.0-stable ruby:3.1 db:sqlite	1m 34s
redmine:5.1-stable ruby:2.7 db:postgres	1m 51s
redmine:5.1-stable ruby:2.7 db:sqlite	1m 39s
redmine:5.1-stable ruby:3.0 db:postgres	1m 31s
redmine:5.1-stable ruby:3.0 db:sqlite	1m 22s
redmine:5.1-stable ruby:3.1 db:postgres	1m 30s
redmine:5.1-stable ruby:3.1 db:sqlite	1m 26s
redmine:5.1-stable ruby:3.2 db:postgres	1m 32s
redmine:5.1-stable ruby:3.2 db:sqlite	1m 25s
redmine:master ruby:3.0 db:postgres	1m 51s
redmine:master ruby:3.0 db:sqlite	1m 38s
redmine:master ruby:3.1 db:postgres	1m 46s
redmine:master ruby:3.1 db:sqlite	1m 40s
redmine:master ruby:3.2 db:postgres	2m 6s
redmine:master ruby:3.2 db:sqlite	1m 32s
	35m 54s

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