chore: remove export_count legacy alias from export state API #128

Job	Run time
mypy	18s
pytest (ubuntu-latest)	20s
API integration tests + coverage (ubuntu-latest)	16s
Verify prod requirements.txt is sufficient	7s
Frontend unit tests (vitest) (windows-latest)	59s
Frontend unit tests (vitest) (ubuntu-latest)	14s
API integration tests + coverage (windows-latest)	33s
pytest (windows-latest)	38s
	3m 25s

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