fix: Correct repo vulnerability alert logic

[stevehipwell]

Corrects logic in #3127

---

Before the change?

• Resource github_repository would call vulnerability alerts endpoint on every modification
• Resource github_repository used ignore_vulnerability_alerts_during_read to allow unprivileged users to skip calling the vulnerability alerts endpoint

After the change?

• Resource github_repository only calls vulnerability alerts endpoint when required
• Resource github_repository only calls vulnerability alerts endpoint during read if the repo response show that the user has the correct permission

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

---

[github-actions]

👋 Hi! Thank you for this contribution! Just to let you know, our GitHub SDK team does a round of issue and PR reviews twice a week, every Monday and Friday! We have a process in place for prioritizing and responding to your input. Because you are a part of this community please feel free to comment, add to, or pick up any issues/PRs that are labeled with Status: Up for grabs. You & others like you are the reason all of this works! So thank you & happy coding! 🚀