Update pubsub.md

[ftyers]

Typo "subscribed"

[codecov-commenter]

Codecov Report

Merging #161 (bafb6c9) into master (b2a7ac7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #161   +/-   ##
=======================================
  Coverage   91.82%   91.82%           
=======================================
  Files          47       47           
  Lines        2384     2384           
=======================================
  Hits         2189     2189           
  Misses        195      195           

Impacted Files	Coverage Δ
src/CoreApi/BlockApi.cs	96.59% <0.00%> (-2.05%)	⬇️
src/BlockExchange/Bitswap1.cs	95.31% <0.00%> (+4.68%)	⬆️

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