[AI-FSSDK] [FSSDK-12368] Remove legacy flag-level holdout fields #1559

Job	Run time
typescript_test	1m 30s
browser_tests (safari)	3m 27s
unit_tests (18)	1m 49s
browser_tests (edge)	7m 52s
integration_tests / test	29s
lint_markdown_files / lint	1m 11s
unit_tests (24)	1m 26s
browser_tests (firefox)	36s
unit_tests (20)	1m 42s
unit_tests (22)	1m 33s
lint	52s
browser_tests (chrome)	7m 21s
fullstack_production_suite / test	28s
Coveralls coverage	3s
	30m 19s

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