Fix Proxmox DataCenter: incorrect build.func url

[rbradley0]

🛠️ Note:
We are meticulous about merging code into the main branch, so please understand that pull requests not meeting the project's standards may be rejected. It's never personal!
🎮 Note for game-related scripts: These have a lower likelihood of being merged.

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✍️ Description

Provide a summary of the changes made and/or reference the issue being addressed.

When originally committed, the Proxmox Datacenter Manager script uses the incorrect URL path for sourcing the build.func script from this repo in turn causing the script to fail when trying to use it.

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Please remove unneeded lines!

• Related Issue: Proxmox-Datacenter Manager #1012
• Related PR: # (if applicable)
• Related Discussion: (if applicable)

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🛠️ Type of Change

Please check the relevant options:

• Bug fix (non-breaking change that resolves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change unexpectedly)
• New script (a fully functional and thoroughly tested script or set of scripts)

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✅ Prerequisites

The following steps must be completed for the pull request to be considered:

• Self-review performed (I have reviewed my code to ensure it follows established patterns and conventions.)
• Testing performed (I have thoroughly tested my changes and verified expected functionality.)
• Documentation updated (I have updated any relevant documentation)

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📋 Additional Information (optional)

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