Fix CI: remove conserver/tests/__init__.py to avoid 'tests' package collision

conserver/ is in pythonpath, so conserver/tests/__init__.py registered a
'tests' package that shadowed the root-level tests/ package. Whichever was
imported first would win, causing the other to fail with:
  ModuleNotFoundError: No module named 'tests.storage'

Removing __init__.py means pytest imports test_link_metrics.py standalone
instead of as part of a 'tests' package. conftest.py is unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: pavanputhra