TensorFlow r2.6 branch cut, June 24

Hi - we would like to announce that a new TF release 2.6.0 is coming up and we will be cutting the r2.6 branch on 6/24/2021 end of day. You can refer to TF 2.6.0 GitHub RELEASE.md document for the current plans for what’s upcoming, and will be updated with changes as we prepare the final release.