style: use unlink consistently, remove unnecessary comment

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: pftg

lib/capybara_screenshot_diff/snap.rb

@@ -60,7 +60,7 @@ def cleanup_diff_artifacts!
         path.sub_ext(".diff.#{format}"),
         path.sub_ext(".heatmap.diff.#{format}"),
         base_path.sub_ext(".diff.#{format}")
-      ].each { |f| f.delete if f.exist? }
+      ].each { |f| f.unlink if f.exist? }
     end
   end
 end

test/unit/snap_manager_test.rb

@@ -67,7 +67,6 @@ class SnapManagerTest < ActiveSupport::TestCase
       @manager.provision_snap_with(snap, source)
       @manager.provision_snap_with(snap, source, version: :base)
 
-      # Simulate reporter artifacts
       diff_path = snap.path.sub_ext(".diff.png")
       base_diff_path = snap.path.sub_ext(".base.diff.png")
       heatmap_path = snap.path.sub_ext(".heatmap.diff.png")