refactor: migrate resource_github_actions_environment_variable to tflog

[texasich]

Replace Go standard log package with HashiCorp structured tflog for consistent logging across the provider.

Changes:

• Replace log import with fmt and add tflog import
• • Convert log.Printf to tflog.Info with structured fields
    Resolves [MAINT] Tracking issue for refactoring logging to use tflog instead of log #3070 (partial — this PR covers one file)

---

Before the change?

resource_github_actions_environment_variable.go uses Go's standard log.Printf for logging, which produces unstructured output inconsistent with the rest of the provider.

After the change?

Logging uses HashiCorp's tflog.Info with structured key-value fields (variable_id), consistent with the pattern established in other migrated files like resource_github_membership.go.

Pull request checklist

• Schema migrations have been created if needed
• - [x] Acceptance tests have been run (no behavioral changes — logging only)
• - [x] Documentation has been updated if needed (N/A — internal refactor)

[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! 🚀

[texasich]

Good catch, thanks @deiga! Fixed in 7a882e5 — now using a static message string with the variable ID passed only through the structured fields map. Also removed the now-unused fmt import.

[texasich]

Friendly ping — is this still on the radar? Happy to rebase if needed.

[deiga]

Hey @texasich 👋
Thanks for using a comment without a ping! 🙏

This is on the radar, yes, but we're short on capacity right now and are focusing on some bigger QoL changes before merging anything else

Sorry for the wait 😬