docs: update the required permissions section of the readme

[ocofaigh]

Description

The current template is confusing and doesn't really match the process of assigning access. I have updated to align more with the UI for setting permissions:

Release required?

• No release
• Patch release (x.x.X)
• Minor release (x.X.x)
• Major release (X.x.x)

Release notes content

Run the pipeline

If the CI pipeline doesn't run when you create the PR, the PR requires a user with GitHub collaborators access to run the pipeline.

Run the CI pipeline when the PR is ready for review and you expect tests to pass. Add a comment to the PR with the following text:

/run pipeline

Checklist for reviewers

• If relevant, a test for the change is included or updated with this PR.
• If relevant, documentation for the change is included or updated with this PR.

For mergers

• Use a conventional commit message to set the release level. Follow the guidelines.
• Include information that users need to know about the PR in the commit message. The commit message becomes part of the GitHub release notes.
• Use the Squash and merge option.

[ocofaigh]

/run pipeline

[terraform-ibm-modules-ops]

🎉 This PR is included in version 1.5.0 🎉

The release is available on GitHub release

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