chore: rename `opening_key` to `verification_key` #381

Job	Run time
Build - x86_64-apple-darwin	1m 14s
Build - aarch64-apple-darwin	1m 15s
Build - x86_64-unknown-linux-gnu	1m 8s
Build - aarch64-unknown-linux-gnu	1m 11s
Build - x86_64-pc-windows-msvc	14m 55s
Build - aarch64-pc-windows-msvc	15m 9s
Test - x86_64-apple-darwin - node@20	37s
Test - aarch64-apple-darwin - node@20	46s
Test - x86_64-unknown-linux-gnu - node@20	46s
Test - aarch64-unknown-linux-gnu - node@20	40s
Test - x86_64-pc-windows-msvc - node@20	38s
Test - aarch64-pc-windows-msvc - node@20	29s
Publish	0s
	38m 48s

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