docs: fix typo in README

[LysandreJik]

Thanks for your work! This PR fixes a tiny typo in the README.

[codecov]

Codecov Report

Merging #222 (3d8ca49) into dev (d5d28b2) will increase coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #222      +/-   ##
==========================================
+ Coverage   34.65%   34.76%   +0.11%     
==========================================
  Files          25       25              
  Lines        2646     2646              
  Branches     1009     1009              
==========================================
+ Hits          917      920       +3     
+ Misses       1694     1691       -3     
  Partials       35       35              

Impacted Files	Coverage Δ
SwiftSyft/Classes/SyftClient.swift	53.33% <0.00%> (+0.76%)	⬆️

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