Fix simple typo: insided -> inside

[timgates42]

Fixes #313

[codecov-io]

Codecov Report

Merging #314 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #314   +/-   ##
=======================================
  Coverage   36.49%   36.49%           
=======================================
  Files          38       38           
  Lines        1307     1307           
=======================================
  Hits          477      477           
  Misses        830      830

Impacted Files	Coverage Δ
patterns/creational/pool.py	48.48% <ø> (ø)	⬆️

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