Follow up: Update and unignore github.com/sigstore/sigstore in open-component-model/ocm

[frewilhelm]

Description

This is a follow-up for open-component-model/ocm#1699.

In open-component-model/ocm#1699 we ignored the package github.com/sigstore/sigstore because it introduced a breaking change (see release notes ) that breaks github.com/sigstore/cosign/v2@v2.6.1:

# github.com/sigstore/cosign/v2/pkg/cosign
Error: /home/runner/go/pkg/mod/github.com/sigstore/cosign/v2@v2.6.1/pkg/cosign/keys.go:143:24: undefined: cryptoutils.ValidatePubKey
Error: /home/runner/go/pkg/mod/github.com/sigstore/cosign/v2@v2.6.1/pkg/cosign/keys.go:152:24: undefined: cryptoutils.ValidatePubKey
Error: /home/runner/go/pkg/mod/github.com/sigstore/cosign/v2@v2.6.1/pkg/cosign/keys.go:163:25: undefined: cryptoutils.ValidatePubKey

A fix is already prepared, see open-component-model/ocm#1699 (comment)

Done Criteria

• Update github.com/sigstore/sigstore and github.com/sigstore/cosign/v2 when available and possible (hopefully the will update 2.6.x too)
• Code has been reviewed by other team members
• Analysis of existing tests (Unit and Integration)
• Unit Tests created for new code or existing Unit Tests updated
• Integration Test Suite updated (includes deletion of existing unnecessary Integration Test and/or creation of new ones if required)