Fix: add GitHub repository collaborators when repository name contains the org name

[ppatel1604]

Resolves #1658

Before the change?

Adding a github_repository_collaborator like below:

terraform {
  required_providers {
    github = {
      source  = "integrations/github"
      version = "~> 5.0"
    }
  }

  required_version = ">= 1.2.0"
}

provider "github" {}

resource "github_repository_collaborator" "main" {
  repository = "my-org/my-repo"
  username   = "kdean-hdai"
  permission = "push"
}

Terraform apply for it returns an error with a status code 404 because the repository attribute is used as it is. During the API call the repo looks something like https://api.github.com/repos/my-org/my-org/my-repo/collaborators/USERNAME instead of https://api.github.com/repos/my-org/my-repo/collaborators/USERNAME

In the request, the org name is used twice which is the cause of the 404 error.

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After the change?

With the change, all the requests made to Github API contains only repository name.

Note
The repository supplied through the TF file is kept as it to avoid any state diff issue. The repository name is only pruned during the Github API Calls.

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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)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[kfcampbell]

Thank you for contributing!