message: Update build instructions
  Summary: Ref T27281
  Reviewers: davidn, #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved
  Maniphest Tasks: T27281
diff: @@ -25,8 +25,8 @@ $ export TF_POPLAR_BASE=/path/to/poplar_sdk/poplar-ubuntu_18_04-x.x.x
  ```
  TensorFlow must be built against a compatible version of the SDK. For example,
  -the "r2.1/release-1.2" branch of TensorFlow for the IPU must be built against
  -Poplar SDK 1.2.
  +the "r2.1/sdk-release-1.3" branch of TensorFlow 2 for the IPU must be built
  +against Poplar SDK 1.3.
  ## Download the TensorFlow source
  