Remove sub_facets field from nested facets schema #851

Job	Run time
Test Collections / Run RSpec	1m 23s
Test Collections Publisher / Run RSpec	1m 34s
Test Contacts Admin / Run RSpec	52s
Test Content Data API / Run RSpec	1m 54s
Test Content Publisher / Run RSpec	3m 18s
Test Content Store / Run RSpec	30s
Test Content Tagger / Run RSpec	1m 49s
Test Email Alert Frontend / Run RSpec	33s
Test Email Alert Service / Run RSpec	12s
Test Feedback / Run RSpec	47s
Test Finder Frontend / Run RSpec	47s
Test Frontend / Run RSpec	3m 3s
Test Government Frontend / Run Minitest	4m 52s
Test HMRC Manuals API / Run RSpec	24s
	21m 58s

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