fix: Remove tests/ from .dockerignore to fix Docker builds

The tests/ directory was incorrectly excluded from Docker builds,
causing the build to fail with 'tests: not found' error.

This fixes the release pipeline Docker image builds.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: lspecian

.dockerignore

@@ -29,7 +29,6 @@ LICENSE
 .travis.yml
 
 # Test files
-tests/
 benches/
 examples/