update set cookie example

[linvis]

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[linvis]

samesite had been removed from method setCookie, see this PR, so update this example in README.md

[codecov]

Codecov Report

Merging #2312 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2312   +/-   ##
=======================================
  Coverage   98.39%   98.39%           
=======================================
  Files          41       41           
  Lines        2304     2304           
=======================================
  Hits         2267     2267           
  Misses         21       21           
  Partials       16       16           

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