Fix bug slicing row/column pairs

[jkanche]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 91.59664% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.53%. Comparing base (e5f7e11) to head (5ef7d91).

Files with missing lines	Patch %	Lines
src/singlecellexperiment/SingleCellExperiment.py	92.47%	8 Missing and 9 partials ⚠️
src/singlecellexperiment/_combineutils.py	57.14%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #78       +/-   ##
===========================================
+ Coverage   68.70%   90.53%   +21.83%     
===========================================
  Files           7        7               
  Lines         639      856      +217     
  Branches       87      142       +55     
===========================================
+ Hits          439      775      +336     
+ Misses        158       48      -110     
+ Partials       42       33        -9     

☔ View full report in Codecov by Harness.
📢 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.