AO3-6774 Create invite_increase_notification mailer preview (#5025) #4974

Job	Run time
rake db:otwseed	1m 17s
rspec spec/controllers	13m 11s
rspec spec/models	5m 34s
rspec --exclude-pattern 'spec/{controllers,models}/*/.rb'	9m 19s
cucumber features/admins	7m 18s
cucumber features/bookmarks	5m 19s
cucumber features/collections	6m 23s
cucumber features/comments_and_kudos	7m 21s
cucumber features/gift_exchanges	6m 48s
cucumber features/importing	2m 52s
cucumber features/other_a	12m 26s
cucumber features/other_b	6m 50s
cucumber features/prompt_memes_a	4m 3s
cucumber features/prompt_memes_b	3m 50s
cucumber features/prompt_memes_c	5m 3s
cucumber features/search	6m 15s
cucumber features/tag_sets	3m 16s
cucumber features/tags_and_wrangling	6m 39s
cucumber features/users	5m 30s
cucumber features/works	13m 49s
	2h 13m 3s

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