Fixes a typo

[Waples]

Fixes a typo in this doc.

[codecov]

Codecov Report

Merging #1454 into master will increase coverage by 0.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1454      +/-   ##
==========================================
+ Coverage   81.18%   81.39%   +0.21%     
==========================================
  Files          27       27              
  Lines        2365     2365              
  Branches      365      365              
==========================================
+ Hits         1920     1925       +5     
+ Misses        354      351       -3     
+ Partials       91       89       -2     

Impacted Files	Coverage Δ
locust/clients.py	95.09% <0.00%> (+4.90%)	⬆️

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