Fix clippy warnings

[phimuemue]

• Overindented list items in doc
• Allow calling last on DoubleEndedIterator in tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.36%. Comparing base (6814180) to head (dcfd571).
Report is 140 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1029      +/-   ##
==========================================
- Coverage   94.38%   94.36%   -0.03%     
==========================================
  Files          48       50       +2     
  Lines        6665     6812     +147     
==========================================
+ Hits         6291     6428     +137     
- Misses        374      384      +10     

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