Clean up lint errors / warnings

[mdekstrand]

This cleans up some lint errors found by GitHub CodeQL.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.11%. Comparing base (4b6bf94) to head (6ccdfa5).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lenskit/batch/_results.py	0.00%	1 Missing ⚠️
src/lenskit/pipeline/config.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #995   +/-   ##
=======================================
  Coverage   89.11%   89.11%           
=======================================
  Files         218      218           
  Lines       15015    15015           
=======================================
  Hits        13381    13381           
  Misses       1634     1634           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.