fix(giskard-oss): PR template message outdated links

[educhesne]

Description

Related Issue

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix

Coding agents

Autonomous agents with no human in the loop must read AUTONOMOUS.md before opening a PR.

PR title: agent-opened PRs must end the title with 🤖🤖🤖🤖 (exactly four robot emojis). Do not omit — that suffix is how the expedited agent PR workflow picks up the PR.

Checklist

• I've read the CODE_OF_CONDUCT.md document.
• I've read the CONTRIBUTING.md guide.
• I've written tests for all new methods and classes that I created.
• I've written the docstring in NumPy format for all the methods and classes that I created or modified.
• I've updated the uv.lock running uv lock (only applicable when pyproject.toml has been
  modified)

[gemini-code-assist]

Code Review

This pull request updates the absolute URLs for the Code of Conduct and Contributing guides in the pull request template to reflect the new repository name and default branch. The reviewer suggests using relative links instead of absolute ones to improve maintainability and prevent similar issues in the future.