fix(install): fix missing dependency signature verification

[LucaGuerra]

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area cli

What this PR does / why we need it:

When using the install command to download an artifact and its dependencies, sometimes signature for dependencies was not properly checked even if a signature entry was present in the index. This fixes it.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alacuku, LucaGuerra

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/falcosecurity/falcoctl/blob/main/OWNERS)~~ [alacuku] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[poiana]

LGTM label has been added.

Git tree hash: 53773e2be4f9d3de1cd81bcbfa6c1b631210fb71

[LucaGuerra]

/milestone v0.8.0

[poiana]

@LucaGuerra: You must be a member of the falcosecurity/falcoctl-maintainers GitHub team to set the milestone. If you believe you should be able to issue the /milestone command, please contact your maintainers of falcosecurity/falcoctl and have them propose you as an additional delegate for this responsibility.

In response to [this](https://github.com/falcosecurity/falcoctl/pull/509#issuecomment-2037157043): >/milestone v0.8.0 Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[alacuku]

/milestone v0.8.0