fix: casing in `exclusiveStartKey` API param #397

Job	Run time
Type check / Type check (3.12)	21s
Lint check / Lint check (3.10)	10s
Type check / Type check (3.10)	17s
Lint check / Lint check (3.13)	8s
Lint check / Lint check (3.12)	10s
Type check / Type check (3.11)	17s
Unit tests / Unit tests (ubuntu-latest, 3.12)	24s
Async dostrings check / Async docstrings check	17s
Docs check / Docs check	1m 5s
Unit tests / Unit tests (windows-latest, 3.12)	58s
Unit tests / Unit tests (ubuntu-latest, 3.10)	22s
Unit tests / Unit tests (ubuntu-latest, 3.13)	29s
Lint check / Lint check (3.11)	11s
Unit tests / Unit tests (windows-latest, 3.11)	49s
Unit tests / Unit tests (ubuntu-latest, 3.11)	22s
Type check / Type check (3.13)	16s
Unit tests / Unit tests (windows-latest, 3.10)	43s
Unit tests / Unit tests (windows-latest, 3.13)	36s
Integration tests / Integration tests (3.11)	42s
Integration tests / Integration tests (3.10)	34s
Integration tests / Integration tests (3.13)	30s
Integration tests / Integration tests (3.12)	34s
Integration tests / Approve integration tests for PRs from forks	0s
Integration tests / Integration tests for PRs from forks	0s
	10m 15s

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