feat: remove unused data in subscription batcher #1203

Job	Run time
ash-ci / mix deps.get	17s
ash-ci / audit	56s
ash-ci / MIX_ENV=test mix.compile	57s
ash-ci / MIX_ENV=dev mix.compile	32s
ash-ci / mix docs	29s
ash-ci / mix sobelow	42s
ash-ci / mix spark.formatter --check	47s
ash-ci / mix format --check-formatted	42s
ash-ci / mix spark.cheat_sheets --check	53s
ash-ci / mix ash.codegen --check	0s
ash-ci / mix credo --strict	43s
ash-ci / mix dialyzer	3m 37s
ash-ci / mix test	1m 9s
ash-ci / mix deps.unlock --check-unused	39s
ash-ci / Deploy docs to GitHub pages.	0s
ash-ci / Release	0s
	12m 23s

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