message: Re-enable variant tests
  Summary:
  Now that we support lowering ops that produce and consume variants,
  we can re-enable these three tests.
  Test Plan: All tests ok
  Reviewers: georgep, jakeh
diff: @@ -61,9 +61,6 @@ CategoricalTest.testStatelessMultinomialIsInRange # No U64
  RandomOpsTest.testRandomNormalIsNotConstant # disable until poplar CPU random works
  RandomOpsTest.testRandomUniformIsNotConstant # disable until poplar CPU random works
  RandomOpsTest.testTruncatedNormalIsNotConstant # disable until poplar CPU random works
  -XlaAddNTest # Disable due to variants in lists
  -WhileTest.testMap # Disable due to variants in lists
  -WhileTest.testMaxItersSimpleV2 # Disable due to variants in lists
  StatelessRandomOpsTest.testDeterminism # poplibs CPU mode does not obey seed
  StatelessRandomOpsTest.testRandomUniformIsInRange # poplar CPU model random uniform int doesn't obey limits
  StatelessRandomOpsTest.testTruncatedNormal # Tests float64
  