Conformance Tests

Update dependency dev.sigstore:protobuf-specs to v0.3.3 #2299

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Run time

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Job	Run time
conformance (11, production)	17m 34s
conformance (11, staging)	2m 4s
conformance (17, production)	15m 47s
conformance (17, staging)	1m 58s
	37m 23s