Remove IRC reference in README

[mcomella]

Pull Request checklist

• [ ] This PR includes thorough tests or an explanation of why it does not
• [ ] This PR includes a CHANGELOG entry or does not need one
• [ ] The UI tests are passing after this PR (./gradlew connectedAmazonWebViewDebugAndroidTest)
• [ ] I have considered adding QA labels on the associated issue (not this PR; qa-ready or qa-denied)

[codecov-io]

Codecov Report

Merging #319 into master will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #319   +/-   ##
=========================================
  Coverage     21.33%   21.33%           
  Complexity      126      126           
=========================================
  Files            92       92           
  Lines          1903     1903           
  Branches        297      297           
=========================================
  Hits            406      406           
  Misses         1459     1459           
  Partials         38       38

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