ci: update sigstore/cosign-installer action to v2.6.0

[sebastien-prudhomme]

This PR contains the following updates:

Package	Type	Update	Change
sigstore/cosign-installer	action	minor	v2.5.1 -> v2.6.0

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Release Notes

sigstore/cosign-installer

v2.6.0

Compare Source

What's Changed

• update action to default cosign to v1.11.0 release by @​cpanato in https://github.com/sigstore/cosign-installer/pull/89
• cleanup dependabot by @​cpanato in https://github.com/sigstore/cosign-installer/pull/90
• default cosign to v1.11.1 by @​cpanato in https://github.com/sigstore/cosign-installer/pull/91
• Bump actions/setup-go from 3.2.1 to 3.3.0 by @​dependabot in https://github.com/sigstore/cosign-installer/pull/92

Full Changelog: sigstore/cosign-installer@v2.5.1...v2.6.0

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