some minor improvements to clustering

[fgregg]

No description provided.

[coveralls]

Coverage decreased (-0.06%) to 64.785% when pulling a3a2ecd on minor_cluster_improvements into dee8105 on main.

[fgregg]

@benchmark

[github-actions]

Benchmarks completed. View runner logs here: https://github.com/dedupeio/dedupe/actions/runs/2289653895
Regex used: ""

All benchmarks:

       before           after         ratio
     [bd606789]       [a3a2ecd9]
     <main>           <minor_cluster_improvements>
             486M             486M     1.00  canonical.Canonical.peakmem_run
        16.2±0.4s        15.8±0.3s     0.98  canonical.Canonical.time_run
  0.9043478260869565  0.9026548672566371     1.00  canonical.Canonical.track_precision
  0.9642857142857143  0.9464285714285714     0.98  canonical.Canonical.track_recall
             186M             186M     1.00  canonical_gazetteer.Gazetteer.peakmem_run(None)
       14.0±0.06s       14.1±0.01s     1.01  canonical_gazetteer.Gazetteer.time_run(None)
  0.9821428571428571  0.9821428571428571     1.00  canonical_gazetteer.Gazetteer.track_precision(None)
  0.9821428571428571  0.9821428571428571     1.00  canonical_gazetteer.Gazetteer.track_recall(None)
             186M             186M     1.00  canonical_matching.Matching.peakmem_run({'threshold': 0.5, 'constraint': 'many-to-one'})
             186M             186M     1.00  canonical_matching.Matching.peakmem_run({'threshold': 0.5})
       13.0±0.02s       12.4±0.05s     0.96  canonical_matching.Matching.time_run({'threshold': 0.5, 'constraint': 'many-to-one'})
       12.3±0.08s        12.4±0.1s     1.00  canonical_matching.Matching.time_run({'threshold': 0.5})
  0.9813084112149533  0.9807692307692307     1.00  canonical_matching.Matching.track_precision({'threshold': 0.5, 'constraint': 'many-to-one'})
  0.9902912621359223  0.9903846153846154     1.00  canonical_matching.Matching.track_precision({'threshold': 0.5})
  0.9107142857142857  0.9107142857142857     1.00  canonical_matching.Matching.track_recall({'threshold': 0.5, 'constraint': 'many-to-one'})
  0.9107142857142857  0.9107142857142857     1.00  canonical_matching.Matching.track_recall({'threshold': 0.5})