remove reference to stale issue in readme

[ersachin3112]

What kind of change does this PR introduce?
documentation

Did you add tests for your changes?
no
If relevant, did you update the documentation?
yes
Summary
The issue is closed - #2222

Does this PR introduce a breaking change?
no

Other information
no

[codecov]

Codecov Report

Merging #2886 (a38d77e) into next (19db829) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             next    #2886   +/-   ##
=======================================
  Coverage   88.76%   88.76%           
=======================================
  Files          48       48           
  Lines         979      979           
  Branches      382      382           
=======================================
  Hits          869      869           
  Misses         74       74           
  Partials       36       36           

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[flyingcircle]

Not necessary. Core contributors can still reach out even if the issue is closed.