Title: #5658: README: Dead social media link remove
Back in 2011 SSSD started using twitter account to broadcast releases.
Last time it happened 13.06.2019 so this account can be considered as
dead. This PR removes link to it from main README.
To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/5658/head:pr5658
git checkout pr5658