docs/index.rst: small enhancement

[kuraga]

No description provided.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (1fcadea) to head (54a5fad).

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Additional details and impacted files

@@            Coverage Diff            @@
##            master      #308   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            3         3           
  Lines          666       666           
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  Hits           666       666           

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[kurtmckee]

Nice. No need to inherit from object in Python 3.

[tkem]

Thanks! Remnants from the time cachetools supported both Python 2.7 and 3.x - surely, there are still some more of these ;-)