Docs: Correcting typos for github_actions_organization_variable resource

[chrisforrette]

Corrects typos in the documentation for the github_actions_organization_variable resource that seem to have been copy/pasted from the docs for github_actions_organization_secret.

---

Behavior

Before the change?

The "Example Usage" section in the docs for the github_actions_organization_variable resource use invalid arguments : secret_name and plaintext_value

After the change?

The secret_name and plaintext_value arguments in "Example Usage" for the github_actions_organization_variable resource have been corrected to variable_name and value, respectively.

---

Additional info

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)
• Added the appropriate label for the given change

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes (Please add the Type: Breaking change label)
• No

If Yes, what's the impact:

• N/A

Pull request type

Please add the corresponding label for change this PR introduces:

• Bugfix: Type: Bug
• Feature/model/API additions: Type: Feature
• Updates to docs or samples: Type: Documentation
• Dependencies/code cleanup: Type: Maintenance

---

[kfcampbell]

Awesome, thank you!