fix: remove non-existent labels from Dependabot configuration

[rhowardstone]

Fixes #722

Problem

Dependabot configuration referenced labels that don't exist in the repository ('dependencies', 'npm', 'github-actions', 'deno'), causing PR creation failures.

Solution

Removed all non-existent label references from .github/dependabot.yml.

Changes

• Removed labels sections from all three package ecosystems (npm, github-actions, gomod)
• Dependabot will now create PRs successfully without label assignment errors

Testing

• Verified configuration syntax is valid
• Removed labels match those reported in issue #722

🤖 Generated with Claude Code (Sonnet 4.5), checked by me

Co-Authored-By: Claude [email protected]