AO3-6676 Remove participant memoization causing Leave button to appear on all collection blurbs #3815

Job	Run time
rake db:otwseed	1m 42s
rspec spec/controllers	10m 29s
rspec spec/models	5m 20s
rspec --exclude-pattern 'spec/{controllers,models}/*/.rb'	4m 51s
cucumber features/admins	5m 17s
cucumber features/bookmarks	4m 22s
cucumber features/collections	5m 37s
cucumber features/comments_and_kudos	6m 0s
cucumber features/gift_exchanges	6m 41s
cucumber features/importing	2m 41s
cucumber features/other_a	9m 41s
cucumber features/other_b	6m 10s
cucumber features/prompt_memes_a	3m 39s
cucumber features/prompt_memes_b	3m 46s
cucumber features/prompt_memes_c	4m 49s
cucumber features/search	6m 15s
cucumber features/tag_sets	3m 37s
cucumber features/tags_and_wrangling	5m 21s
cucumber features/users	4m 17s
cucumber features/works	13m 22s
	1h 53m 57s

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