[BUG]: fix github repository file id escaping

[deiga]

Resolves #3335

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Before the change?

• Terraform would throw an error if filePath in github_repository_resource contained a colon
  • This was introduced by me in [MAINT] Fixup github_repository_file #3175 when I changed the ID generation code

After the change?

• Terraform successfully operates on resources when filePath in github_repository_resource contains a colon

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

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[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! 🚀

[stevehipwell]

Have we tested this doesn't break existing IDs? It looks OK, but worth checking. Also should we add this to the next minor release milestone as we can always cherry pick it into a patch if required?