chore(deps): update dependency sigstore/cosign to v3.1.3

[renovate]

This PR contains the following updates:

Package	Type	Update	New value	References	Sourcegraph
sigstore/cosign	uses-with	patch	v3.1.3	source

Test plan: CI should pass with updated dependencies. No review required: this is an automated dependency update PR.

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Release Notes

sigstore/cosign (sigstore/cosign)

v3.1.3

Compare Source

What's Changed

This release resolves GHSA-fx35-mq7g-6g98, a verification bypass using an unexpected public key in a legacy bundle.

• Auto-detect default digest algorithm for public keys in #​5019
• fix(pkcs11key): return an error instead of panicking when no key pair matches in #​5022
• Supporting OCI Signing with X.509 Certificate Chain in #​4614
• test(inspect): replace mock TSA client usage with local timestamp response generator in #​5021
• fix: prevent shell completions for various options not taking filenames in #​5032
• fix(blob): compare file checksums case-insensitively in #​5036
• Verification bypass via public key in legacy bundle (GHSA-fx35-mq7g-6g98) in #​5040

Full Changelog: sigstore/cosign@v3.1.2...v3.1.3

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