docs: update links to Semaphore pages

[TomFern]

Description

This change only affects the Trivy Docs

At Semaphore, we have changed the Semaphore domain from semaphoreci.com to semaphore.io. We have also added new docs with an integration with Trivy. This change updates the links to the correct domains and URLs

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Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).