Fix configuration

[waybackarchiver]

Rename WAYBACK_DISCORD_TOKEN to WAYBACK_DISCORD_BOT_TOKEN

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Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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Checklist

• I have followed the contributing guidelines of this project as mentioned in CONTRIBUTING.md
• I have checked to ensure there aren't other open Pull Requests for the same update/change?
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes needed to the documentation