Update release refs for 7.5-stable

[jamis]

Updates references to the release actions to the canonical repo.

[Copilot]

Pull Request Overview

This PR updates GitHub Actions workflow references from a personal fork (jamis/drivers-github-tools) to the canonical repository (mongodb-labs/drivers-github-tools) and updates the version from a feature branch to the stable v3 tag. The changes also remove the now-unnecessary SILK_ASSET_GROUP environment variable and its corresponding parameter in the publish action.

Key Changes

• Updated action references from jamis/drivers-github-tools (feature branch) to mongodb-labs/drivers-github-tools@v3 (stable release)
• Removed SILK_ASSET_GROUP environment variable and its usage in the publish step

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