readme grammar change

[yaovi-a]

Creating my first PR of many others: there'll be other unsolicited grammar changes.

[CLAassistant]

All committers have signed the CLA.

[tsachiherman]

please sign the CLAassistant

[codecov-commenter]

Codecov Report

Merging #2938 (19a9744) into master (e4842fc) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2938      +/-   ##
==========================================
- Coverage   47.30%   47.28%   -0.02%     
==========================================
  Files         356      356              
  Lines       57244    57244              
==========================================
- Hits        27081    27070      -11     
- Misses      27098    27106       +8     
- Partials     3065     3068       +3     

Impacted Files	Coverage Δ
ledger/blockqueue.go	82.18% <0.00%> (-1.73%)	⬇️
catchup/peerSelector.go	98.95% <0.00%> (-1.05%)	⬇️
catchup/service.go	68.57% <0.00%> (-0.78%)	⬇️
ledger/acctupdates.go	62.50% <0.00%> (-0.60%)	⬇️
network/wsPeer.go	74.93% <0.00%> (+0.55%)	⬆️
cmd/tealdbg/debugger.go	73.86% <0.00%> (+1.00%)	⬆️

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[yaovi-a]

Just signed it.