Updated implementation links in vigenere_cipher.md

[SpiderMath]

Description

Added implementation links in Vigenere Cipher (C#, Julia, Rust, Java)

Closes #{ISSUE_ID}

Checklist

• A description of the changes in this PR is mentioned above.
• All the new and existing checks pass.
• No plagiarized, duplicated, or repetitive documentation that has been directly copied from another source.
• If it's a new explanation, it contains solid, understandable, and accessible information.
• I have read the whole contributing guidelines and agree to the Code of Conduct.

Screenshots (if any)

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Note to reviewers

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[appgurueu]

I wish we could just link to https://the-algorithms.com/de/algorithm/vigenere-cipher, but there's another: https://the-algorithms.com/de/algorithm/vigenere. Standardization is hard...

[github-actions]

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