Add missing ostruct require, fix system tests on CI #2624

Job	Run time
lint	39s
postgres_test (gemfiles/rails_master.gemfile, 3.3, 1)	1m 57s
javascript_test	31s
postgres_test (gemfiles/rails_7.1_postgresql.gemfile, 3.3)	2m 0s
mongodb_test (gemfiles/mongoid_6.gemfile)	1m 57s
mongodb_test (gemfiles/mongoid_7.gemfile)	1m 58s
system_tests	2m 13s
test (Gemfile, 3.2)	1m 44s
test (Gemfile, 2.7)	1m 46s
test (gemfiles/rails_7.0.gemfile, 3.1)	2m 20s
test (gemfiles/rails_master.gemfile, 3.2)	2m 31s
test (gemfiles/rails_7.0.gemfile, 3.2)	2m 12s
test (gemfiles/rails_7.1.gemfile, 3.3)	2m 17s
test (gemfiles/rails_master.gemfile, 3.3, 1)	2m 21s
test (gemfiles/rails_master.gemfile, 3.3, 1, 1)	2m 23s
	28m 49s

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