[fix]: skip file-specifc schema data for directory

[prestonvasquez]

Resolves #1930

---

Before the change?

Using a directory as the file in a data block will result in a segmentation violation, e.g.

data "github_repository_file" "directory" {
  repository = local.repo
  branch     = local.branch
  file       = "vendor"
}

After the change?

This change is based on the observation that file information cannot be extracted from a slice of github.RepositoryContent. Therefore, if the "file" parameter passed to the "dataSourceGithubRepositoryFileRead" function refers to a directory, we should skip attempting to retrieve file-specific content.

Pull request checklist

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

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

---

[nickfloyd]

Non breaking change since the behavior was a seg violation and not a clean exit. The behavior is as intended with this PR.

[nickfloyd]

Thank you @prestonvasquez for theses commits! ❤️